Power supply control device for on-vehicle electrical loads

ABSTRACT

A power supply control device for on-vehicle electric loads is proposed, the control device being capable of detecting breakages at a plurality of electrical loads, a positive side wiring thereof, a negative side wiring thereof, and a commutation circuit. Energization of electrical loads from driving power supply is controlled using switching elements. Anode terminals of commutation diodes connected in parallel with the electrical loads are connected to a load ground by an external common negative line or external individual negative lines. A breakage abnormality at the external common negative line or external individual negative lines is detected by negative line breakage abnormality detection circuit. Load currents at the electrical loads are detected by current detection resistors and current detecting differential amplifier circuits, and it is determined that there is an individual abnormality when a detected current is greatly different from a target current.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power supply control device forelectrical loads used in an on-vehicle electronic control apparatus and,particularly, to a power supply control device which detects anybreakage and shorting abnormality of a load power supply circuit forelectrical loads connected to a vehicle body at a negative terminalthereof.

2. Description of the Related Art

There are various types of power supply control devices for on-vehicleelectrical loads which control an on-off duty factor of a switchingelement connected between a driving power supply and an electrical loadsuch that a target current to be passed agrees with a current detectedby a current detection resistor. For example, such control devicesinclude current control devices for linear solenoids which require acurrent constantly varying in a wide range and current control devicesfor fuel injection electromagnetic valves which are kept open by aconstant low current after being opened rapidly.

Some of such current control devices employ an internal feedback controlmethod in which a microprocessor generates a target current command anda switching drive command according to a deviation between the targetcurrent command a detected current, and others employ an externalfeedback control method in which a microprocessor only generates atarget current command and in which a switching drive command isgenerated by a deviation integrating circuit provided outside themicroprocessor in accordance with a deviation between the target commandcurrent and a detected current.

In either control method, a commutation diode is connected in parallelwith a series circuit formed by a current detection resistor and anelectrical load. When a switching element is turned off, the commutationdiode returns a load current which has been passed through theelectrical load until that time, whereby the load current is smoothedand the generation of a surge voltage is suppressed.

In any of the current control devices, a ground circuit inside thecurrent control device and a DC driving power supply, which is anon-vehicle battery, are both connected to a vehicle both at negativeterminals thereof. A negative terminal of an electrical load may beconnected in various ways.

For example, in the case of a current detector for an inductive loaddisclosed in Patent Document 1 listed below, a switching element isconnected to a positive terminal of a linear solenoid constituting anelectrical load, and a negative terminal of the electrical load is firstled into a current control device and is then connected to a vehiclebody outside the current detector through a current detection resistor.An anode terminal of a commutation diode is connected to a groundcircuit inside the current detector.

In the case of a linear solenoid fault detector disclosed in PatentDocument 2 listed below, a switching element and a current detectionresistor are connected to a positive terminal of a linear solenoidconstituting an electrical load, and a negative terminal of theelectrical load is connected to a vehicle body outside the faultdetector. An anode terminal of a commutation diode is connected to aground circuit inside the fault detector.

Patent Document 1: JP-2003-75476A, in particular, FIG. 1 and abstract

Patent Document 2: JP-2000-114039A, in particular, FIG. 1 and abstract

(01) Explanation of Technical Problems in the Prior Arts

In the case of the current detector disclosed in Patent Document 1,since the current detection resistor is connected to the negativeterminal of the electrical load, a problem arises in that connectors arerequired for a positive pole side wiring for connecting the electricalload to the switching element and for a negative pole side wiring forconnecting the load to the current detection resistor.

When there is a shorting fault of the electrical load or a ground faultthat is interference or contact between the positive pole side wiring ofthe electrical load and the vehicle body, an over-current flows throughthe switching element because of a very small current limitingresistance incorporated in the switching element. Thus, even if theswitching element is quickly turned off, a possibility of a temporaryover-stress on the switching element still remains.

Further, when there is breakage of a wiring connecting the currentdetector connected to the negative terminal of the electrical load tothe vehicle body or there is a contact failure of a connector, anexcessive surge voltage is applied to the interior of the currentdetector, which can result in breakage of the current detector.

In the case of the fault detector disclosed in Patent Document 2, thenumber of wirings for the electrical load is reduced. In addition, evenwhen a shorting fault of the electrical load or a ground fault of thepositive pole side wiring occurs, the switching element can be safelyprotected by suppressing any over-current through the switching elementwith the current detection resistor and quickly turning the switchingelement off.

However, when the witching element opens, since the load currentreturned to the commutation diode returns through the ground circuitinside the fault detector, the ground potential in the fault detectorcan fluctuate to cause erroneous operations attributable to noises.

(02) Object of the Present Invention

It is an object of the invention to suggest a power supply controldevice for an on-vehicle electrical load which serves as simple measuresto provide protection against a shorting fault of the electrical load orand a ground fault of a wiring on a positive pole side of the load andwhich is configured such that a load current will not be superimposed onan internal ground circuit of a power supply control unit.

SUMMARY OF THE INVENTION

The invention provides a power supply control device for on-vehicleelectrical loads, comprising a power supply control unit including aplurality of load power supply circuits for supplying power from a DCdriving power supply to a plurality of electrical loads respectivelythrough switching elements, a plurality of load commutation circuits forcommutating load currents to the electrical loads, and a power supplycontrol circuit for supplying an energization command output to theswitching elements. The load power supply circuits, the load commutationcircuits, and the power supply control circuit are contained in ahousing of the power supply control unit. The power supply controldevice is characterized as follows. Commutation diodes are provided inthe respective commutation circuits and each of the commutation diodesis connected in parallel with the corresponding electrical load to causea current which have been flowing through the electrical load to flowback when the switching element of the load power supply circuit isturned off. The commutation diodes are connected to a vehicle bodyoutside the housing separately from an internal ground circuit of thepower supply control unit by an external common negative line. The powersupply control circuit includes an individual abnormality detectioncircuit, a negative line breakage abnormality detection circuit,abnormality processing means, and abnormality history storing means. Thepower supply control circuit is configured by using a microprocessor.The microprocessor is configured to operate in conjunction with anon-volatile program memory in which at least a control program servingas an energization command means for the switching elements is stored, adata memory, a RAM memory for arithmetic processes, and a multi-channelA-D converter. The individual abnormality detection circuit includes aplurality of power supply state detection circuits for detecting amountsof power supplied to the electrical loads and means for determining anindividual abnormal state when the amount of power supplied to a certainelectrical load among the electrical loads deviates from a target amountof supplied power, the individual abnormal state is either breakage orshorting of at least one of the electrical load, a positive side wiringof the electrical load, a negative side wiring of the electrical load,and the switching element associated with the electrical load. Thenegative line breakage abnormality detection circuit is a circuit fordetermining a breakage abnormality of the external common negative lineby detecting that an electric potential on an anode side of eachcommutation diode is different from an electric potential at theinternal ground circuit of the power supply control unit. Theabnormality processing means is means for stopping the energizationcommand output to the switching elements when at least either anindividual abnormality or a breakage abnormality at the external commonnegative line is detected and for providing a notice of the abnormality.The abnormality history storing means is means for storing and savingthe history of occurrence of individual abnormalities and breakageabnormalities at the external common negative line in the data memorywith identification of the abnormalities.

In the power supply control device for on-vehicle electrical loadsaccording to the invention, each of the commutation diodes is connectedin parallel with the corresponding electrical load and the commutationdiodes are connected to the vehicle body outside the power supplycontrol unit separately from the internal ground circuit of the powersupply control unit through the external negative line. As a result,neither load current nor commutation current flows to the internalground circuit of the power supply control unit, which is advantageousin that the electrical potential at the internal ground circuit can bestabilized to allow the power supply control circuit of the power supplycontrol unit to operate with stability. Any breakage abnormality andshorting abnormality at the electrical loads, the positive side wiringsthereof, the negative side wirings thereof, and the switching elementsis detected by the individual abnormality detection circuit. Anybreakage at the external negative line associated with the commutationdiodes is detected by the negative line breakage abnormality detectioncircuit. Measures are taken against those abnormalities, and theabnormalities are identified and stored by the abnormality historystoring means. The efficiency of maintenance and inspection cantherefore be advantageously improved by reading the history informationat the time of maintenance and inspection.

The above-described object, features and advantages of the inventionwill be more clearly understood from the following detailed descriptionof the invention with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general circuit diagram of Embodiment 1 of a power supplycontrol device for on-vehicle electrical loads according to theinvention;

FIG. 2 is a detailed circuit diagram of a major part of Embodiment 1;

FIG. 3 is a detailed circuit diagram of a negative line breakageabnormality detection circuit in Embodiment 1;

FIG. 4 is a flow chart for explaining operations of Embodiment 1;

FIG. 5 is a general circuit diagram of Embodiment 2 of a power supplycontrol device for on-vehicle electrical loads according to theinvention;

FIG. 6 is a detailed circuit diagram of a major part of Embodiment 2;

FIG. 7 is a detailed circuit diagram of a negative line breakageabnormality detection circuit in Embodiment 2;

FIG. 8 is a flow chart for explaining operations of Embodiment 2;

FIG. 9 is a general circuit diagram of Embodiment 3 of a power supplycontrol device for on-vehicle electrical loads according to theinvention; and

FIG. 10 is a detailed circuit diagram of a major part of Embodiment 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (11) Configurationof Embodiment 1

A configuration of Embodiment 1 of a power supply control device foron-vehicle electrical loads according to the invention will now bedescribed. FIG. 1 is a general circuit diagram of the power supplycontrol device for on-vehicle electrical loads in Embodiment 1.

The power supply control device for on-vehicle electrical loads ofEmbodiment 1 shown in FIG. 1 includes a power supply control unit 100A,a DC driving power supply 101, and a load circuit 103. The DC drivingpower supply 101 is an on-vehicle battery which generates a drivingpower supply voltage Vb, for example, in the range from 10 to 16 volts.A negative terminal of the DC driving power supply 101 is connected to avehicle body at a power supply ground GND0. The term “connection to avehicle body” means connection to the body of a vehicle or common groundconnection at a vehicle. The power supply control unit 100A is suppliedwith power from the DC driving power supply 101 and controls a group ofon-vehicle electric loads. The group of on-vehicle electrical loadsincludes a load circuit 103. The load circuit 103 includes a pluralityof electrical loads which are, for example, electrical loads 103 a, 103b, and 103 c in FIG. 1. The electrical loads 103 a, 103 b, and 103 c areinductive on-vehicle electrical loads. A negative terminal of each ofthe electrical loads 103 a, 103 b, and 103 c is connected to the vehiclebody at a load ground GND3 through a negative side wiring 103N. Thepower supply control unit 100A controls supply of power from the DCdriving power supply 101 to the electrical loads 103 a, 103 b, and 103c.

For example, the power supply control unit 100A constitutes atransmission control device for an automobile, and the electrical loads103 a, 103 b, and 103 c are linear solenoids used in a transmission foran automobile. The power supply control unit 100A includes amicroprocessor 120A as a primarily element, controls load currentssupplied from the DC driving power supply 101 to the electrical loads103 a, 103 b, and 103 c using energization command outputs DR1 to DR3,and drives an alarm indicator 105 for providing a notice of anabnormality using an abnormality notice output ER.

A group of inputs from switches such as sensor switches and operationswitches which are not shown is connected to a digital input port of themicroprocessor 120A of the power supply control unit 100A through aconnector and an interface circuit which are not shown. A group ofanalog inputs from various analog sensors which are not shown isconnected to an analog input port of the microprocessor 120A through aconnector and an interface circuit which are not shown. A group ofelectrical loads such as actuators and indicators which are not shown isconnected to an output port of the microprocessor 120A through aconnector and an interface circuit which are not shown. The group ofelectrical loads includes the electrical loads 103 a to 103 c and thealarm indicator 105 for providing a notice of an abnormality.

The power supply control unit 100A is contained in a sealed housing 100a. The power supply control unit 100A includes a power supply inputterminals ES1, ES2, and ES3, a unit ground terminal GND, three loadoutput terminals LD1, LD2, and LD3, a common terminal COM, and aninternal ground circuit GND2. The power supply input terminals ES1 toES3, the unit ground terminal GND, the load output terminals LD1 to LD3,and the common terminal COM are disposed in the housing 100 a, theelements being electrically insulated from the housing 100 a.

The power supply input terminal ES1 is connected to a positive terminalof the DC driving power supply 101 through a load power supply relaycontact 102 b and supplied with power from the DC driving power supply101 through the load power supply relay contact 102 b. The power supplyinput terminal ES2 is directly connected to the positive terminal of theDC driving power supply 101. The power supply input terminal ES3 isconnected to the positive terminal of the DC driving power supply 101through a power supply switching relay contact 102 a. The unit groundterminal GND is connected to the housing 100 a and connected to thevehicle body along with the housing 100 a at the unit ground GND1. Theload output terminals LD1, LD2, and LD3 are directly connected topositive terminals of the electrical loads 103 a, 103 b, and 103 cthrough positive side wirings 103P of the respective loads. Negativeterminals of the electrical loads 103 a, 103 b, and 103 c are connectedto the vehicle body at the load ground GND3 through negative sidewirings 103N of the loads. The common terminal COM is commonly connectedwith negative pole side wirings 103N of the electrical loads 103 a to103 c by an external negative line, which is an external common negativeline 104 in Embodiment 1, and the common terminal is connected to thevehicle body at the load ground GND3. The internal ground circuit GND2is a common ground circuit which extends inside the power supply controlunit 100A and which is disposed, for example, on a circuit substrateforming part of the power supply control unit 100A.

Instead of extending the external common negative line 104 from thecommon terminal COM to the negative pole side wirings 103N andconnecting them, the wirings may be connected to the vehicle body at aseparated ground GND4 provided in the vicinity of the common terminalCOM through a shorter external common negative line 104. In this case,connection between the separated ground GND4 and the load ground GND3 isestablished by the vehicle body. The distance between the separatedground GND4 and the load ground GND3 is smaller than the distancebetween the separated ground GND4 and the unit ground GND2. As a result,resistance between the separated ground GND4 and the load ground GND3 issmaller than resistance between the separated ground GND4 and the unitground GND2, and fluctuations of an electric potential at the vehiclebody attributable to commutation at the electrical loads 103 a to 103 ccan therefore be kept small.

A load power supply circuit SPLa and a load commutation circuit SWLa areformed in association with the electrical load 103 a. Similarly, loadpower supply circuits SPLb and SPLc and load commutation circuits SWLband SWLc are formed in association with the electrical loads 103 b and103 c, respectively. The load power supply circuits SPLa, SPLb, and SPLcare circuits for supplying power from the DC driving power supply 101 tothe electrical loads 103 a, 103 b, and 103 c. In the power supplycontrol unit 100A, the load power supply circuit SPLa is formed betweenthe power supply input terminal ES1 and the load output terminal LD1;the load power supply circuit SPLb is formed between the power supplyinput terminal ES1 and the load output terminal LD2; and the load powersupply circuit SPLc is formed between the power supply input terminalES1 and the load output terminal LD3. The load commutation circuitsSWLa, SWLb, and SWLc are commutation circuits for commutating a loadcurrent flowing through the electrical loads 103 a, 103 b, and 103 cwhen the load current is interrupted. In the power supply control unit100A, the load commutation circuit SWLa is formed between the load powersupply circuit PSLa and the common terminal COM; the load commutationcircuit SWLb is formed between the load power supply circuit SPLb andthe common terminal COM; and the load commutation circuit SWLc is formedbetween the load power supply circuit SPLc and the common terminal COM.

The power supply control unit 100A incorporates a power supply controlcircuit PCNTA in addition to the load power supply circuits SPLa to SPLcand the load commutation circuits SWLa to SWLc. The power supply controlcircuit PCNTA is primarily constituted by the microprocessor 120A. Thepower supply control circuit PCNTA includes a control power supplycircuit 110, switching circuits 130 a to 130 c, commutation circuits1400 a to 1400 c, individual abnormality detection circuit IADETA, and anegative line breakage abnormality detection circuit 160A. Theindividual abnormality detection circuit IADETA detects individualabnormalities at the electrical loads 103 a to 103 c, and the negativeline breakage abnormality detection circuit 160A detects abnormalitiesat the external common negative line 104.

The switching circuits 130 a to 130 c are disposed at the load powersupply circuits SPLa to SPLc, respectively. The switching circuit 130 ais connected in series with the electrical load 103 a to the load powersupply circuit SPLa provided between the power supply input terminal ES1and the load output terminal LD1 to control a load current at theelectrical load 103 a. The switching circuit 130 b is connected inseries with the electrical load 103 b to the load power supply circuitSPLb provided between the power supply input terminal ES1 and the loadoutput terminal LD2 to control a load current at the electrical load 103b. The switching circuit 130 c is connected in series with theelectrical load 103 c to the load power supply circuit SPLc providedbetween the power supply input terminal ES1 and the load output terminalLD3 to control a load current at the electrical load 103 c.

The individual abnormality detection circuit IADETA is constituted bypower supply state detection circuits PDETAa to PDETAc provided inassociation with the electrical loads 103 a to 103 c, respectively, andthe microprocessor 120A. The power supply state detection circuit PDETAaassociated with the electrical load 103 a includes a current detectioncircuit 140 a, a current detecting differential amplifier circuit 150 a,and a load voltage monitoring circuit 170 a. Similarly, the power supplystate detection circuits PDETAb and PDETAc associated with theelectrical loads 103 b and 103 c include current detection circuits 140b and 140 c, current detecting differential amplifier circuits 150 b and150 c, and load voltage monitoring circuits 170 b and 170 c,respectively.

The current detection circuits 140 a to 140 c include current detectionresistors 141 a to 141 c. The current detection resistor 141 a isconnected in series with the electrical load 103 a to the load powersupply circuit SPLa provided between the switching circuit 130 a and theload output terminal LD1 to detect the load current at the electricalload 103 a. The current detection resistor 141 b is connected in serieswith the electrical load 103 b to the load power supply circuit SPLbprovided between the switching circuit 130 b and the load outputterminal LD2 to detect the load current at the electrical load 103 b.The current detection resistor 141 c is connected in series with theelectrical load 103 c to the load power supply circuit SPLc providedbetween the switching circuit 130 c and the load output terminal LD3 todetect the load current at the electrical load 103 c. Details of thecurrent detection circuit 140 a will be described later with referenceto FIG. 2.

The load commutation circuit SWLa is formed between a point ofconnection between the switching circuit 130 a and the current detectionresistor 141 a and the common terminal COM. The load commutation circuitSWLb is formed between a point of connection between the switchingcircuit 130 b and the current detection resistor 141 b and the commonterminal COM. The load commutation circuit SWLc is formed between apoint of connection between the switching circuit 130 c and the currentdetection resistor 141 c and the common terminal COM.

The commutation circuits 1400 a to 1400 c are disposed in the loadcommutation circuits SWLa to SWLc, respectively. The commutation circuit1400 a includes a commutation diode 146 a. The commutation diode 146 ais connected in parallel with the series circuit formed by the currentdetection resistor 141 a and the electrical load 103 a to commutate theload current flowing through the electrical load 103 a. The commutationcircuit 1400 b includes a commutation diode 146 b. The commutation diode146 b is connected in parallel with the series circuit formed by thecurrent detection resistor 141 b and the electrical load 103 b tocommutate the load current flowing through the electrical load 103 b.The commutation circuit 1400 c includes a commutation diode 146 c. Thecommutation diode 146 c is connected in parallel with the series circuitformed by the current detection resistor 141 c and the electrical load103 c to commutate the load current flowing through the electrical load103 c. The commutation diodes 146 a to 146 c are connected to the commonterminal COM at respective anode terminals A and connected to the loadpower supply circuits SPLa, SPLb, and SPLc at respective cathodeterminals K. Details of the commutation circuit 1400 a will be describedlater with reference to FIG. 2.

The microprocessor 120A of the power supply control circuit PCNTA issupplied with power from the control power supply circuit 110. Thecontrol power supply circuit 110 is connected to the power supply inputterminals ES2 and ES3. The power supply input terminal ES2 is directlyconnected to the positive terminal of the DC driving power supply 101,and the power supply input terminal ES3 is connected to the positiveterminal of the DC driving power supply 101 through the power supplyswitching relay contact 102 a. The control power supply circuit 110generates a DC voltage Vcc of, for example, 5.0 volts and supplies it tothe microprocessor 120A when the power supply switching relay contact102 a is on. When the power supply switching relay contact 102 a isturned off, the circuit 110 generates a DC voltage of, for example, 2.8volts and supplies it to a partial area of a RAM memory 122, no powerbeing supplied to the microprocessor 120A.

The control power supply circuit 110 is connected to the internal groundcircuit GND2 of the power supply control unit 100A. The circuitconnecting the control power supply circuit 110 to the internal groundcircuit GND2 is connected to the unit ground terminal GND. The unitground terminal GND is also connected to the housing 100 a and connectedto the vehicle body through the ground GND1. Voltage dividing resistors111 and 112 are connected in series with the power supply input terminalES2. The voltage dividing resistors 111 and 112 form a power supplyvoltage measuring circuit 115 for the DC driving power supply 101, and adriving power supply voltage Vd measured by the same is supplied to themicroprocessor 120A.

The microprocessor 120A is bus-connected to a non-volatile programmemory 121A constituted by, for example, a non-volatile flash memorywhich can be electrically erased at once to allow writing and which canbe read, a RAM memory 122 for arithmetic processes, a data memory 123constituted by a non-volatile EEPROM which can be electrically writtenand read byte by byte, and a multi-channel A-D converter 124. Themicroprocessor is configured for mutual cooperation with those elements.The data memory 123 may be configured using part of the non-volatileprogram memory 121A.

The microprocessor 120A generates the digital energization commandoutputs DR1 to DR3 and the abnormality notice output ER. Themicroprocessor 120A receives monitoring voltages Ef1 to Ef3 and thedriving power supply voltage Vd as analog inputs and receives alarmsignals OV1 to OV3 and alarm signals SV1 to SV3 as digital inputs. Theenergization command outputs DR1 to DR3 are supplied to the switchingcircuits 130 a to 130 c, respectively. The alarm indicator 105 forproviding a notice of an abnormality is driven by the abnormality noticeoutput ER.

The switching circuit 130 a is turned on/off under control of theenergization command output DR1 generated by the microprocessor 120A,and the circuit supplies the electrical load 103 a with a load voltageproportionate to an energization duty that is the ratio of the on-timeto the on/off period. Similarly, the switching circuits 130 b and 130 care turned on/off under control of the energization command outputs DR2and DR3, respectively, generated by the microprocessor 120A, and thecircuits supply the electrical loads 103 b and 103 c with load voltagesproportionate to energization duties that are the ratios of the on-timesto the on/off periods thereof. The load currents through the electricalloads 103 a to 103 c are proportionate to the energization duties of theswitching circuits 130 a to 130 c. Details of the switching circuit 130a will be described later with reference to FIG. 2.

The current detecting differential amplifier circuit 150 a of the powersupply state detection circuit PDETAa performs differentialamplification of a voltage across the current detection resistor 141 aand supplies a monitoring voltage Ef1 proportionate to a load currentIf1 flowing through the electrical load 103 a to the analog input portof the microprocessor 120A. Similarly, the current detectingdifferential amplifier circuits 150 b and 150 c of the power supplystate detection circuits PDETAb and PDETAc perform differentialamplification of voltages across the current detection resistors 141 band 141 c and supply monitoring voltages Ef2 and Ef3 proportionate toload currents If2 and If3 flowing through the electrical loads 103 b and103 c to the analog input port of the microprocessor 120A. Details ofthe current detecting differential amplifier circuit 150 a will bedescribed with reference to FIG. 2.

Based on a program to serve as a negative feedback control means storedin the non-volatile program memory 121A, the microprocessor 120Aexercises control to vary the energization duty of the energizationcommand output DR1 such that the amount of supplied power thus detected,which is specifically the load current If1, agrees with the targetamount of supplied power which is specifically a target load currentIs1. Similarly, control is exercised to vary the energization duties ofthe energization command outputs DR2 and DR3 such that the detected loadcurrents If2 and If3 agree with target load currents Is2 and Is3,respectively.

The load voltage monitoring circuit 170 a monitors the voltage at theload output terminal LD1 to which the positive side wiring 103P of theelectrical load 103 a is connected, compares the voltage at the loadoutput terminal LD1 with a predetermined threshold voltage, and suppliesthe alarm signals OV1 and SV1 to the microprocessor 120A. Similarly, theload voltage monitoring circuits 170 b and 170 c monitor the voltages atthe load output terminals LD2 and LD3 to which the positive side wirings103P of the respective electrical loads 103 b and 103 c are connected,compares the voltages at the load output terminals LD2 and LD3 withpredetermined threshold voltages, and supplies the alarm signals OV1,OV3, SV2, and SV3 to the microprocessor 120A. Details of the loadvoltage monitoring circuit 170 a will be described later with referenceto FIG. 2.

The negative line breakage abnormality detection circuit 160A detectsbreakage of the external common negative line 104 and breakage of thenegative line attributable to a contact failure of the common terminalCOM and supplies an alarm signal MNT to the microprocessor 120A. Detailsof the negative line breakage abnormality detection circuit 160A will bedescribed later with reference to FIG. 3.

FIG. 2 shows details of major parts of the power supply control unit101A in FIG. 1. Specifically, FIG. 2 shows the load power supply circuitSPLa, the load commutation circuit SWLa, the switching circuit 130 a,the commutation circuit 1400 a, the current detection circuit 140 a, thecurrent detecting differential amplifier circuit 150 a, and the loadvoltage monitoring circuit 170 a which are associated with theelectrical load 103 a. The switching circuits 130 b and 130 c, thecommutation circuits 1400 b and 1400 c, the current detection circuits140 b and 140 c, the current detecting differential amplifier circuits150 b and 150 c, and the load voltage monitoring circuits 170 b and 170c associated with the electrical loads 103 b and 103 c are configuredsimilarly to the switching circuit 130 a, the commutation circuit 1400a, the current detection circuit 140 a, the current detectingdifferential amplifier circuit 150 a, and the load voltage monitoringcircuit 170 a, respectively.

Referring to FIG. 2, the switching circuit 130 a comprises the switchingelement 131 a as a primary element. In addition to the switching element131 a, the switching circuit 130 a includes a PNP transistor 132 a,various resistors 133 a, 134 a, 135 a, 136 a, and 139 a, an NPNtransistor 137 a, and a block diode 138 a. The switching element 131 ais a power transistor, and it is specifically constituted by a P-channelfield effect CMOS transistor. The driving power supply voltage Vb isapplied to a source terminal S of the switching element 131 a, and adrain terminal D of the element is connected to the load output terminalLD1 through the current detection resistor 141 a. A voltage clampingdiode 1311 is connected between the source terminal S and the drainterminal D of the switching element 131 a. The voltage clamping diode1311 is a constant voltage diode whose anode terminal A is connected tothe drain terminal D of the switching element 131 a and whose cathodeterminal K is connected to the source terminal S of the switchingelement 131 a, the diode suppressing the voltage at the switchingelement 131 a when the element is off. A leakage resistor 149 a having ahigh resistance is further connected between the source terminal S andthe drain terminal D of the switching element 131 a. The leakageresistor 149 a supplies the electrical load 103 a with such a very smallload current that the electrical load 103 a is not activated when theswitching element 131 a is off.

An emitter terminal E of the PNP transistor 132 a is connected to anoutput terminal of a voltage step-up circuit 113 a including acharge-pump circuit which is supplied with driving power supply voltageVb. A collector terminal C of the transistor is connected to a gateterminal G of the switching element 131 a through a collector resistor133 a. A gate resistor 134 a is connected between the gate terminal Gand the drain terminal D of the switching element 131 a. A stabilizingresistor 135 a for off-state is connected between the emitter terminal Eand a base terminal B of the PNP transistor 132 a. The base terminal Bis connected to a collector terminal C of the NPN transistor 137 athrough a base resistor 136 a.

An emitter terminal E of the NPN transistor 137 a is connected to theinternal ground terminal GND2 of the power supply control unit 100Athrough the block diode 138 a. The energization command output DR1 fromthe microprocessor 120A is supplied to a base terminal B of the NPNtransistor 137 a through the driving resistor 139 a. When theenergization command output DR1 becomes a logical level “H”, the NPNtransistor 137 a, the PNP transistor 132 a, and the switching element131 a are turned on. When the energization command output DR1 becomes alogical level “L”, those elements are turned off. A leakage resistor 149a having a high resistance is parallel-connected between the sourceterminal S and the drain terminal D of the switching element 131 a tosupply a very small load current to the electrical load 103 a even whenthe switching element 131 a is off.

A bypass resistor 147 a is connected in parallel with the commutationdiode 146 a of the commutation circuit 1400 a. The bypass resistor 147 aforms a load voltage dividing circuit 1410 a in combination with theleakage resistor 149 a connected between the source terminal S and thedrain terminal D of the switching element 131 a.

The current detection circuit 140 a includes the current detectionresistor 141 a as a primary element. In addition to the currentdetection resistor 141 a, the current detection circuit 140 a includes afirst series resistor 142 a, a third series resistor 143 a, and firstand second negative voltage suppressing diodes 144 a and 145 a. Apositive potential side of the current detection resistor 141 a isconnected to the internal ground circuit GND2 through a series circuitformed by the first series resistor 142 a and the first negative voltagesuppressing diode 144 a. A negative potential side of the currentdetection resistor 141 a is connected to the internal ground circuitGND2 through a series circuit formed by the third series resistor 143 aand the second negative voltage suppressing diode 145 a. The first andsecond negative voltage suppressing diodes 144 a and 145 a are connectedto the internal ground circuit GND2 at respective anode terminals A andare connected to the first series resistor 142 a and the third seriesresistor 143 a at respective cathode terminals K. The cathode terminal Kof the commutation diode 146 a is connected to the positive potentialside of the current detection resistor 141 a, and the anode terminal Aof the commutation diode 146 a is connected to the common terminal COM.

The current detecting differential amplifier circuit 150 a includes adifferential amplifier 151 a as a primary element, the differentialamplifier operating on the control power supply voltage Vcc output fromthe control power supply circuit 110 as a power supply voltage of thesame. In addition to the differential amplifier 151 a, the differentialamplifier circuit 150 a includes various resistors 152 a, 153 a, 154 a,155 a, 156 a, 157 a, and 158 a, and a smoothing capacitor 159 a. Anon-inverting input of the differential amplifier 151 a is connected tothe positive potential side of the current detection resistor 141 athrough the second series resistor 152 a and the first series resistor142 a of the current detection circuit 140 a. An inverting input of thedifferential amplifier 151 a is connected to the negative potential sideof the current detection resistor 141 a through a fourth series resistor153 a and the third series resistor 143 a of the current detectioncircuit 140 a.

A combined resistance R2 provided by the first series resistor 142 a andthe second series resistor 152 a connected in series with each other anda combined resistance R3 provided by the third series resistor 143 a andthe fourth series resistor 153 a connected in series with each other aredesigned to have theoretical design values that satisfy R2=R3. Thenon-inverting input of the differential amplifier 151 a is connected tothe internal ground circuit GND2 through the voltage dividing resistor154 a which has a resistance R4, and the inverting input of thedifferential amplifier 151 a is connected to an output terminal of thedifferential amplifier 151 a through the negative feedback resistor 155a which has a resistance R5. The resistances R4 and R5 have theoreticaldesign values that satisfy R4=R5.

A bias voltage V0 is applied to the non-inverting input of thedifferential amplifier 151 a through the bias resistor 156 a which has aresistance R6, and the bias voltage V0 is applied to the inverting inputof the differential amplifier 151 a through the bias resistor 157 awhich has a resistance R7. The resistances R6 and R7 have theoreticaldesign values that satisfy R6=R7. The bias voltage V0 is a predeterminedpositive voltage applied to each input terminal of the differentialamplifier 151 a to offset a negative voltage of about 1 volt applied bythe commutation diode 146 a to each input terminal of the differentialamplifier 151 a. The output terminal of the differential amplifier 151 ais connected to the analog input port of the microprocessor 120A throughthe output terminal 158 a. The smoothing capacitor 159 a is charged fromthe output resistor 158 a to form a smoothing circuit.

The value of the monitoring voltage Ef1 that is an output voltage fromthe differential amplifier circuit 150 a having such a configuration andthe value of the load current If1 satisfy the relationship expressed byExpression (1) shown below. Similarly to the current detectingdifferential amplifier circuit 150 a shown in FIG. 2, the currentdetecting differential amplifier circuits 150 b and 150 c generatesmonitoring voltages Ef2 and Ef3 as expressed by Expressions (2) and (3)below and input them to the microprocessor 120A.

Ef1=R1×(R5/R3)×If1  (1)

Ef2=R1×(R5/R3)×If2  (2)

Ef3=R1×(R5/R3)×If3  (3)

where R1 represents the resistance of the current detection resistors141 a, 141 b, and 141 c; R5 represents the resistance of the negativefeedback resistor 155 a; and R3 represents the combined seriesresistance of the third and fourth series resistors 143 a and 153 a.

The load voltage monitoring circuit 170 a includes the first and secondcomparison/determination circuit 171 a and 271 a as primary elements. Inaddition to the first and second comparison/determination circuits 171 aand 271 a, the load voltage monitoring circuit 170 a includes variousresistors 172 a, 173 a, 174 a, 176 a, 177 a, 178 a, 272 a, 276 a, 277 a,and 278 a, inverting logic elements 179 a and 279 a, a clip diode 274 a,and smoothing capacitors 175 a and 275 a. A non-inverting input of thefirst comparison/determination circuit 171 a is connected to a point ofconnection between the voltage dividing resistors 173 a and 174 athrough the input resistor 172 a, and the clip diode 274 a is connectedin parallel with the resistor 174 a of the voltage dividing resistors173 a and 174 a which are series-connected with each other. An anodeterminal A of the clip diode 274 a is connected to the internal groundcircuit GND2, and a cathode terminal K of the diode is connected to thepoint of connection between the voltage dividing resistors 173 a and 174a. The other of the pair of voltage dividing resistors 173 a and 174 a,i.e., the voltage dividing resistor 173 a is connected to the loadoutput terminal LD1, and a voltage proportionate to the load voltage Vf1applied to the electrical load 103 a is applied to the voltage dividingresistor 174 a. The smoothing capacitor 175 a is connected to thenon-inverting input of the first comparison/determination circuit 171 a.An inverting input of the first comparison/determination circuit 171 ais connected to a point of connection between the voltage dividingresistors 176 a and 177 a for setting a first threshold voltageproportionate to the driving power supply voltage Vb.

A design satisfying Expression (4) shown below is employed where R173and R174 represent the resistances of the voltage dividing resistors 173a and 174 a, respectively; R176 and R177 represent the resistances ofthe voltage dividing resistors 176 a and 177 a, respectively; R149represents the resistance of the leakage resistor 149 a; and R147represents the resistance of the bypass resistor 147 a.

[R147/(R147+R149)]×[R174/(R174+R173)]>R177/(R177+R176)  (4)

Therefore, when the switching element 131 a is off due to a breakage atthe electrical load 103 a, the first comparison/determination circuit171 a has an output logical level “H” at which the alarm signal OV1 fora breakage abnormality is generated. An output terminal of the firstcomparison/determination circuit 171 a is connected to an alarm inputterminal OV1 of the microprocessor 120A through the output resistor 178a. The inverting logic element 179 a is driven by the energizationcommand output DR1 from the microprocessor 120A, and a logic inversionoutput of the element is connected to the alarm input terminal OV1.

When there is no breakage at the electrical load 103 a connected to theload output terminal LD1, the load voltage during an off-time of theswitching element 131 a is very small, and the output of the firstcomparison/determination circuit 171 a is at the logical level “L”.However, in case there is a breakage at the electrical load 103 a or incase there is a breakage at the positive side wiring 103P or negativeside wiring 103N of the electrical load 103 a, the driving power supplyvoltage Vb divided by the load dividing circuit 1410 a or the leakageresistor 149 a and the bypass resistor 147 a is applied to the loadoutput terminal LD1. As a result, the output logical level of the firstcomparison/determination circuit 171 a becomes “H”, and the alarm signalOV1 inputs the occurrence of the breakage abnormality to themicroprocessor 120A. When the logical level of the energization commandoutput DR1 is “H” and the switching element 131 a is on, the logicallevel of the alarm signal OV1 does not become “H” because of theinverting logic element 179 a.

A non-inverting input of the second comparison/determination circuit 271a is connected to the point of connection between the voltage dividingresistors 173 a and 174 a through the input resistor 272 a, and thesmoothing capacitor 275 a is connected to the non-inverting input of thesecond comparison/determination circuit 271 a. An inverting input of thesecond comparison/determination circuit 271 a is connected to the pointof connection between the voltage dividing resistors 276 a and 277 awhich set a second threshold voltage proportionate to the driving powersupply voltage Vb.

A design satisfying Expression (5) shown below is employed where R276and R277 represent the resistances of the voltage dividing resistors 276a and 277 a.

[R174/(R174+R173)]>R277/(R277+R276)  (5)

Therefore, when a shorting abnormality occurs at the switching element131 a or when the positive side wiring 103P is in contact with a powersupply line connected to the positive terminal of DC driving powersupply 101, the second comparison/determination circuit 271 a has anoutput logical level “H” at which the alarm signal SV1 for a shortingabnormality is generated.

An output terminal of the second comparison/determination circuit 271 ais connected to an alarm input terminal SV1 of the microprocessor 120Athrough the output resistor 278 a. The inverting logic element 279 a isdriven by the energization command output DR1 from the microprocessor120A, and a logic inversion output of the element is connected to thealarm input terminal SV1.

When there is no breakage at the electrical load 103 a connected to theload output terminal LD1, the load voltage during an off-time of theswitching element 131 a is very small, and the output of the secondcomparison/determination circuit 271 a is at the logical level “L”.However, in case there is a power line shorting that the positive sidewiring 103P of the electrical load 103 a is contacted to the powersupply line connected to the positive terminal of the driving powersupply 101 and in case the switching element 131 a has a shortingabnormality, a voltage substantially equal to the driving power supplyvoltage Vb is applied to the load output terminal LD1. As a result, theoutput logical level of the second comparison/determination circuit 271a becomes “H”, and the alarm signal SV1 inputs the occurrence of thepower line shorting or the shorting abnormality of the switching element131 a to the microprocessor 120A. However, when the logical level of theenergization command output DR1 is “H” and the switching element 131 ais on, the logical level of the alarm signal SV1 does not become “H”because of the inverting logic element 279 a.

The negative line breakage abnormality detection circuit 160A in FIG. 1will now be described with reference to FIG. 3. Referring to FIG. 3, thenegative line breakage abnormality detection circuit 160A includes adetermination element 161 constituted by a PNP transistor which issupplied with the control power supply voltage Vcc. A collector terminalC of the determination element 161 is connected to the internal groundcircuit GND2 through a collector resistor 162 and connected to the alarmsignal terminal MNT of the microprocessor 120A through an outputresistor 163 a. An integrating capacitor 163 b is charged from theoutput resistor 163 a to form a smoothing circuit. A stabilizingresistor 164 for off-state is connected between an emitter terminal Eand a base terminal B of the determination element. The base terminal Bof the determination element 161 is connected to the common terminal COMthrough a base resistor 165 and, a current-limiting resistor 166, and aconstant voltage diode 167, and the anode terminals A of commutationdiodes 146 a, 146 b, and 146 c are connected to the common terminal COM.

An energization operating voltage of the constant voltage diode 167 is avoltage which is lower than the suppressed voltage of the switchingelements 131 a, 131 b, and 131 c during an off-time thereof attributableto the voltage clamping diodes 1311 and which is higher than the controlpower supply voltage Vcc. An anode terminal A of a clip diode 168 isconnected to the internal ground circuit GND2, and a cathode terminal Kof the diode is connected to a point of connection between the baseresistor 165 and the current-limiting resistor 166.

When there is a breakage at the external common negative line 104connected to the common terminal COM, e.g., when the switching element131 a changes from on to off, the determination element 161 is caused tobe conducting by a surge current which flows from the power supply lineof the control power supply voltage Vcc to the load output terminal LD1via an emitter/base circuit of the determination element 161, the baseresistor 165, the current-limiting resistor 166, the constant voltagediode 167, the commutation diode 146 a, and the current detectionresistor 141 a. The element thus changes the logical level of the alarmsignal MNT to “H” to input the occurrence of the negative line breakageabnormality.

A series circuit formed by a driving resistor 261 and a drivingtransistor 262 is connected to a base circuit of the determinationelement 161. The driving transistor 262 is an NPN transistor. A seriescircuit formed by a block diode 263 and a detection resistor 264 isconnected to a base circuit of the driving transistor 262, and astabilizing resistor 265 for off-state and a clip diode 266 areconnected between a base terminal B and an emitter terminal E of thedriving transistor 262. An anode terminal A of the block diode 263 isconnected to the common terminal COM, and a cathode terminal K of thediode is connected to the detection resistor 264. An anode terminal A ofthe clip diode 266 is connected to the internal ground circuit GND2, anda cathode terminal K of the diode is connected to the base terminal B ofthe driving transistor 262.

When a breakage occurs at the external common negative line 104connected to the common terminal COM with any of the switching elements131 a, 131 b, and 131 c in the on-state, the transistor 262 is turned onthrough any of the bypass resistors 147 a, 147 b, and 147 c and thedetection resistor 264, the determination element 161 is turned onaccordingly to change the logical level of the alarm signal MNT to “H”.Therefore, the determination element 161 generates the alarm signal MNTby detecting negative electric potentials generated at the anodeterminals A of the commutation diodes 146 a, 146 b, and 146 c when theload currents to the electrical loads 103 a, 103 b, and 103 c areinterrupted or detecting positive electric potentials generated at theanode terminals A of the commutation diodes 146 a, 146 b, and 146 c bythe bypass resistors 147 a, 147 b, and 147 c during a period in whichthe switching elements 131 a, 131 b, and 131 c are on. When the commonterminal COM is properly connected to the vehicle body by the externalcommon negative line 104, no electric potential is generated at theanode terminals A of the commutation diodes 146 a, 146 b, and 146 c, andthe logical level of the alarm signal MNT generated by the determinationelement 161 is “L” which indicates a normal state.

(12) Effects and Operations of Embodiment 1

Effects and operations of Embodiment 1 of the invention shown in FIGS. 1to 3 will now be described.

Referring to FIG. 1, when a power supply switch which is not shown isturned on, the power supply switching relay contact 102 a is turned onto apply the driving power supply voltage Vb to the control power supplycircuit 110, and the control power supply circuit 110 generates thecontrol power supply voltage Vcc and supplies it to the microprocessor120A. When the microprocessor 120A starts operating, the load powersupply relay contact 102 b is turned on by an energization circuit whichis not shown.

Based on an operation control program stored in the non-volatile programmemory 121A, the microprocessor 120A determines which of the electricalloads in the electrical load circuit 103 is to be supplied with a loadcurrent and determines the amount of the load current and thereafterexercises control over the load current based on a control program toserve as a negative feedback control means stored in the non-volatileprogram memory 121A.

A description will now be made on an operation performed by the negativefeedback control means to control the load current If1 at the electricalload 103 a. Operations for controlling the load currents If2 and If3 atthe electrical loads 103 b and 103 c are similar to the operation forcontrolling the load current at the electrical load 103 a. The negativefeedback control means controls the turning on/off of the switchingelement 131 a by generating the energization command output DR1 having avariable duty γ1 in accordance with an integrated value of a deviationbetween the energization target current Is1 for the electrical load 103a and the load current If1 detected by the current detectingdifferential amplifier circuit 150 a.

The load current If1 flows through the load power supply circuit SPLbwhen the switching element 131 a is on. Specifically, the current startsfrom the positive terminal of the DC driving power supply 101 andarrives at the vehicle body through the load power supply relay contact102 b, power supply input terminal ES1, the switching element 131 a, thecurrent detection resistors 141 a, the load output terminal LD1, thepositive side wiring 103P, the electrical load 103 a, the negative sidewiring 103N and the load ground GND3, and then flows from the vehiclebody to a path arriving at the negative terminal of the DC driving powersupply 101 through the power supply ground GND0. In this case, the loadcurrent If1 does not flow to the internal ground circuit GND2 in thepower supply control unit 100A at all.

The load current If1 flows through the load commutation circuit SWLawhen the switching element 131 a is off. Specifically, the currentstarts from the negative terminal of the electrical load 103 a andcirculates through a path formed by the negative side wiring 103N, theexternal common negative line 104, the common terminal COM, thecommutation diode 146 a, the current detection resistor 141 a, the loadoutput terminal LD1, and the positive side wiring 103P back to thepositive terminal of the electrical load 103 a. In this case again, theload current If1 does not flow to the internal ground circuit GND2 ofthe power supply control unit 100A at all. When the external commonnegative line is connected to the vehicle body at the position of theseparated ground GND4 provided in the vicinity of the common terminalCOM of the power supply control unit 100A instead of extending the lineto the position of the load ground GND3, the vehicle body is usedinstead of the external common negative line 104 as a path forenergization extending from the load ground GND3 up to the separatedground GND4. In this case again, the load current If1 does not flow tothe internal ground circuit GND2 in the power supply control unit 100Aat all.

Let us now assume that the common terminal COM and the external commonnegative line 104 are not provided and that the anode terminal A of thecommutation diode 146 a is connected to the internal ground circuit GND2of the power supply control unit 100A. Referring to the path ofcirculation of the load current If1 commutated when the switchingelement 131 a is off, the current starts from the negative terminal ofthe electrical load 103 a and circulates through a path formed by thenegative side wiring 103N, the load ground GND3, the unit groundterminal GND1, the internal ground circuit GND2, the commutation diode146 a, the current detection resistor 141 a, the load output terminalLD1, and the positive side wiring 103P back to the positive terminal ofthe electrical load 103 a. In this case, a problem arises in that acommutation surge current flows into the internal ground circuit GND2 ofthe power supply control unit 100A to cause fluctuations of the electricpotential at the internal ground circuit GND2.

In Embodiment 1, the anode terminals A of the commutation diodes 146 ato 146 c of the commutation circuits 1400 a to 1400 c are connected tothe common terminal COM, and the common terminal COM is connected to thevehicle body outside the power supply control unit 100A, which makes itpossible to prevent the load currents If1, If2, and If3 from flowinginto the internal ground circuit GND2 of the power supply control unit100A. On the contrary, when there is a contact failure of the commonterminal COM or a breakage abnormality at the external common negativeline 104, the commutating function of the commutation diodes 146 a, 146b, and 146 c is deteriorated, which results in another problem in thatan induced surge voltage is generated by inductive components of theelectrical loads 103 a, 103 b, and 103 c when the switching elements 131a, 131 b, and 131 c are turned off.

The induced surge voltage is suppressed to, for example, about 50 voltsby the voltage clamping diodes 1311 for suppressing an off-voltageprovided at the switching elements 131 a, 131 b, and 131 c. However, thesuppressed surge voltage will be applied to all internal circuits of thepower supply control unit 100A which are connected between the internalground circuit GND2 and the load output terminals LD1, LD2, and LD3.

In the switching circuit 130 a shown in FIG. 2, the block diode 138 aassociated with the switching element 131 a blocks a countercurrentattributable to the suppressed surge voltage. In the current detectioncircuit 140 a, the first and second negative voltage suppressing diodes144 a and 145 a suppress the input electric potentials of thedifferential amplifier 151 a to negative electric potentials of, forexample, about 1 volt that is the forward voltage of the first andsecond negative voltage suppressing diodes 144 a and 145 a. The firstand third series resistors 142 a and 143 a suppress a surge currentwhich circulates from the unit ground GND1 to the load output terminalLD1 via the internal ground circuit GND2 and the first or secondnegative voltage suppressing diode 144 a or 145 a, thereby suppressingfluctuations of the electric potential at the internal ground circuitGND2.

Similarly, in the load voltage monitoring circuit 170 a shown in FIG. 2,the clip diode 274 a suppresses the input electric potentials of thefirst and second comparison/determination circuits 171 a and 271 a tonegative electric potentials of, for example, about 1 volt that is theforward voltage of the clip diode 274 a. The voltage dividing resistor173 a suppresses a surge current which circulates, from the unit groundGND1 to the load output terminal LD1 via the internal ground circuitGND2 and the clip diode 274 a, thereby suppressing fluctuations of theelectric potential at the internal ground circuit GND2. Effects andoperations of the elements associated with the electrical loads 103 band 103 c are similar to those in the case of the electrical load 103 a.

In the negative line breakage abnormality detection circuit 160A shownin FIG. 3, the clip diode 168 suppresses the negative side electricpotential of the base resistor 165 to a negative electric potential of,for example, about 1 volt that is the forward voltage of the clip diode168. The current-limiting resistor 166 and the constant voltage diode167 suppress a surge current which circulates from the unit ground GND1to the load output terminal LD1 via the internal ground circuit GND2 andthe clip diode 168, thereby suppressing fluctuations of the electricpotential at the internal ground circuit GND2. The block diode 263blocks the circulation of a surge current via the detection resistor264, whereas the clip diode 266 protects the driving transistor 262.

The operating voltage of the constant voltage diode 167 is a value lowerthan the surge voltage suppressed by the voltage clamping diode 1311 forsuppressing an off-voltage provided at the switching elements 131 a, 131b, and 131 c and higher than the control power supply voltage Vcc.Therefore, in a normal state, a base current is prevented from flowingto the determination element 161 by the clip diode 168 or the constantvoltage diode 167, and the logical level of the alarm signal MNT istherefore “L”. However, when there is a breakage at the external commonnegative line 104 connected to the common terminal COM, thedetermination element 161 is caused to be conducting by a surge currentwhich flows from the base resistor 165 up to the load output terminalLD1 through the current-limiting resistor 166, the constant voltagediode 167, the commutation diode 146 a, and the current detectionresistor 141 a, and the logical level of the alarm signal MNT becomes“H” to input the occurrence of a breakage abnormality at the negativeline. When the switching elements 131 a, 131 b, and 131 c are in theon-state, the determination element 161 is caused to be conducting bythe transistor 262 which is energized and driven from the bypassresistors 147 a, 147 b, and 147 c through the block diode 263 and thedetection resistor 264.

FIG. 4 is a flow chart for explaining operations of Embodiment 1. Theoperations will now be described with reference to FIG. 4. In FIG. 4,step 400 is a step at which load current control forming a part ofvarious control flows of the microprocessor 120A is started. Thesubsequent step 401 is a step which constitutes a negative line breakageabnormality determination means for determining a breakage abnormalityat the negative line, and it is determined at step 401 whether thenegative line breakage abnormality detection circuit 160A has detected abreakage abnormality at the negative line by monitoring the state ofinput of the alarm signal MNT. When a breakage abnormality has occurredat the negative line and the result of the determination at step 401 istherefore YES, the process proceeds to step 411. If the result of thedetermination at step 401 is NO, the process proceeds to step 402.

Step 411 is a step which constitutes an abnormality processing meansand, more specifically, an all output stopping means and an abnormalitynotification command means. At step 411, all of the energization commandoutputs DR1, DR2, and DR3 are stopped, and the alarm output ER isgenerated to activate the alarm indicator 105. The subsequent step 413is a step which constitutes an abnormality history storing means. Step413 writes and stores the information of the occurrence of a breakageabnormality at the negative line in the data memory 123. The subsequentstep 460 is a current control operation ending step. At step 460, themicroprocessor 120A executes control operations other than currentcontrol, and the operation starting step 400 is activated again after apredetermined time passes to repeat the series of control operations.

Step 402 is a step which constitutes a load number setting/updatingmeans. At step 402, load numbers n (n=a, b, c, and so on) for aplurality of electrical loads 103 a, 103 b, 103 c, and so on arespecified and sequentially updated and specified. The subsequent step403 is a step which constitutes a target current reading means. At step403, a target current value Isn associated with an electrical load 103 nhaving a load number n specified at step 402 is read. The target currentvalue Isn is determined based on another control program which is notshown. The subsequent step 404 is a step which constitutes a loadcurrent reading means. At step 404, a load current value Ifn of theelectrical load 103 n detected by a differential amplifier 150 n forcurrent detection associated with the load number n specified at step402 is read. The subsequent step 405 is a step which constitutes aninitial operation determination means. At step 405, it is determinedwhether an initial operation is being performed based on a determinationmade at a subsequent step 407 on whether an initialization complete flaghas been set. When an initial operation is being performed and theresult of the determination at step 405 is therefore YES, the processproceeds to step 406. If the result of the determination at step 405 isNO, the process proceeds to step 408.

Step 406 is a step which constitutes a check starting means. At step406, an energization duty γn of an energization command output DRnassociated with the electrical load 103 n is nullified to perform aninitial check. The subsequent step 420 a is a step which constitutes apower line shorting alarm determination means. At step 420 a, it isdetermined by a load voltage monitoring circuit 170 n associated withthe electrical load 103 n specified at step 402 whether an alarm signalSVn has been generated. When the alarm signal SVn has been generated andthe result of the determination at step 420 a is therefore YES, theprocess proceeds to step 421. If the result of the determination at step420 a is NO, the process proceeds to step 420 b. Step 420 b is a stepwhich constitutes a breakage alarm determination means. At step 420 b,it is determined by the load voltage monitoring circuit 170 n whether analarm signal OVn has been generated or not. When the alarm signal OVnhas been generated and the result of the determination at step 420 b isYES, the process proceeds to step 421. If the result of thedetermination at step 420 b is NO, the process proceeds to step 407.Step 421 is a step which constitutes an abnormality processing means,more specifically, a relevant output stopping means and an abnormalitynotification command means. At step 421, the relevant energizationcommand output DRn associated with the electrical load 103 n is stopped,and an alarm output ER is generated to activate the alarm indicator 105.The subsequent step 423 is a step which constitutes an abnormalityhistory storing means, more specifically, a categorized abnormalityhistory storing means. Step 423 writes and stores the information of thegeneration of the alarm signal SVn or alarm signal OVn in the datamemory 123. Specifically, step 423 stores a shorting abnormality at aswitching element 131 n and a power line shorting abnormality that anyof the positive side wirings 103P of the electrical loads 103 n iscontacted to the power supply line connected to the positive terminal ofthe DC driving power supply 101 when the logical level of the alarmsignal SVn is “H” with the energization command output DRn stopped. Whenthe alarm signal OVn has been generated, a breakage abnormality at anyof the electrical load 103 n, the positive wiring 103P, and the negativewiring 103N is stored. Step 423 is followed by current control operationending step 460.

Step 407 is a step which constitutes an initial setting means. At thisstep, the energization duty γn is set at an initial value γn0, and theinitialization complete flag is set. The process then proceeds to step408. The energization duty γn0 set at step 407 is a value given byExpression (6) shown below where Rc represents the resistance of theelectrical load 103 n at an average temperature and Vb represents thevalue of the driving power supply voltage calculated from a measuredpower supply voltage input Vd.

γn0=Rc×Isn/Vb  (6)

The initialization complete flag set at step 407 is reset when thetarget current value Isn read at step 403 is zero, and the result of thedetermination at step 405 is YES when the initialization complete flaghas been reset.

Step 408 is a step constituting a load resistance estimation means. Atstep 408, a load resistance Rn of the electrical load 103 n iscalculated by Expression (7) shown below based on the currentenergization duty γn of the specified electrical load 103 n, the drivingpower supply voltage Vb, and the load current value Ifn, the step beingfollowed by step 430.

Rn=γn×Vb/Ifn  (7)

Step 430 is a step which constitutes an under-resistance determinationmeans. At step 430, it is determined whether the load resistance Rncalculated at step 408 is an abnormal value which is smaller than aminimum resistance Rmin of the electrical load 103 n at lowtemperatures. When the resistance Rn is smaller than the minimum valueRmin and the result of the determination at step 430 is therefore YES,the process proceeds to step 431. If the result of the determination atstep 430 is NO, the process proceeds to step 440. Step 431 is a stepwhich constitutes an abnormality processing means, more specifically, arelevant output stopping means and an abnormality notification commandmeans. At step 431, the relevant energization command output DRn isstopped, and the alarm output ER is generated to activate the alarmindicator 105. The subsequent step 432 is a step which constitutes aconfirmative determination means. At step 432, it is determined whetherthe load current Ifn has become zero as a result of the stoppage of theenergization command output DRn at step 431. When the load current Ifnhas been properly restored to zero and the result of the determinationat step 432 is therefore YES, the process proceeds to step 433 b. If theresult of the determination at step 432 is NO, the process proceeds tostep 433 a.

Steps 433 a and 433 b are steps which constitute an abnormality historystoring means, more specifically, a categorized abnormality historystoring means. At steps 433 a and 433 b, abnormality information basedon the result of the confirmative determination at step 432 is writtenand stored in the data memory 123 when an under-resistance is determinedat step 430. At step 433 a, the occurrence of a shorting abnormality atthe switching element 131 n in the duration of an energization commandto the switching element 131 n is recorded as abnormality historyinformation. Abnormality history information recorded at step 433 b isthe fact that either shorting abnormality at the electrical load 103 nor grounding abnormality that is contact between the positive wiring103P and the vehicle body has occurred and that no shorting abnormalityhas occurred at the switching element 131 n in the duration of theenergization command to the switching element 131 n. Steps 433 a and 433b are followed by current control operation ending step 460.

Step 440 is a step which constitutes an over-resistance determinationmeans. At step 440, it is determined whether the load resistance Rncalculated at step 408 is an abnormal value which is greater than amaximum resistance Rmax of the electrical load 103 n at hightemperatures. When the resistance Rn is an abnormal value greater thanthe maximum value Rmax and the result of the determination at step 440is therefore YES, the process proceeds to step 441. If the result of thedetermination at step 440 is NO, the process proceeds to step 450 a.Step 441 is a step which constitutes an abnormality processing means,more specifically, a relevant output stopping means and an abnormalitynotification command means. At step 441, the relevant energizationcommand output DRn is stopped, and the alarm output ER is generated toactivate the alarm indicator 105. The subsequent step 443 is a stepwhich constitutes an abnormality storing means, more specifically, acategorized abnormality history storing means. At step 443, informationof the occurrence of an over-resistance abnormality detected at step 440is written and stored in the data memory 123. The occurrence of anover-resistance abnormality means that a breakage abnormality at theelectrical load 103 n, a breakage abnormality at the positive sidewiring 103P, a breakage abnormality at the negative side wiring 103N, apower line shorting abnormality at the positive side wiring 103P or abreakage abnormality at the switching element 131 n has occurred in theduration of an energization command to the switching element 131 n. Theoccurrence of any of those abnormalities is stored in the data memory123 as abnormality history information. Step 443 is followed by currentcontrol operation ending step 460.

Step 450 a is a step which constitutes a correction value calculationmeans for calculating a correction value Δγn for the currentenergization duty γn. Step 450 a is executed when the resistance isdetermined to be proper at steps 430 and 440 and the results of thedeterminations at steps 430 and 440 are both YES. At step 450 a, thecorrection value Δγn for correcting the current energization duty γn byincreasing or decreasing the same is calculated according to the signand magnitude of the deviation between the target current value Isn readat step 403 and the load current value Ifn read at step 404. Thesubsequent step 450 b is a step which constitutes means for settingcorrection to be made to the current energization duty γn. At step 450b, the correction value Δγn is algebraically added to the currentenergization duty γn. Processing block 450 formed by steps 450 a and 450b constitutes a negative feedback control means.

Step 450 b is followed by current control operation ending step 460. Atcurrent control operation ending step 460, the microprocessor 120Aexecutes control operations other than current control, and theoperation starting step 400 is activated again after a predeterminedtime passes to repeat the series of control operations.

The control operation flow chart in FIG. 4 will now be schematicallydescribed. Step 401 is a step for monitoring the state of input of thealarm signal MNT to determine whether any negative breakage abnormalityhas been detected by the negative line breakage abnormality detectioncircuit 160A. The negative line breakage abnormality detection circuit160A is enabled for abnormality detection when at least one of theplurality of electrical loads 103 a to 103 c is conducting. At step 413,a code number for a breakage abnormality at the negative line is stored,but no electrical load is specified.

Steps 420 a and 420 b monitor the state of input of the alarm signalsSVn and OVn to determine whether any abnormality has been detected bythe load voltage monitoring circuit 170 n. The load voltage monitoringcircuit 170 n is enabled for abnormality detection when the energizationcommand output DRn to the switching element 131 n is stopped. At step423, a code number for a shorting abnormality at the switching element131 n and a code number for a power line shorting abnormality at thepositive side wiring 103P of the electrical load 103 n are stored whenthe alarm signal SVn is at the logical level “H”, but it can not bespecified which of the abnormalities has occurred. At step 423, a codenumber for a breakage abnormality at the electrical load 103 n and abreakage at either the positive side wiring 103P or negative side wiring103N of the electrical load 103 n is stored when the alarm signal OVn isgenerated but the alarm signal SVn is not generated. The position of thebreakage cannot be identified.

Steps 430 and 440 execute abnormality determination using software bymonitoring the resistance Rn of the electrical load 103 n. Anyunder-resistance or over-resistance is determined by comparing theresistance Rn with the minimum resistance value Rmin or the maximumresistance value Rmax when the energization command output DRn isgenerated. A code number for a shorting abnormality at the switchingelement 131 n is stored at step 433 a, and a code number for a shortingabnormality at the electrical load 103 n and a code number for agrounding abnormality at the positive side wiring 103P of the electricalload 103 n are stored at step 433 b. It cannot be specified which of ashorting abnormality at the electrical load 103 n and a groundingabnormality at the positive side wiring 103P has occurred.

When there is a shorting abnormality at the switching element 131 nwhich disallows the switching element 131 n to be turned off, a currenthigher than the target current value Isn flows through the electricalload 103 n. Although the microprocessor 120A decreases the energizationduty γn in order to make the current closer to the target current valueIsn, the load current Ifn stays at the maximum value instead of beingdecreased however the energization duty γn is decreased because of theshorting at the switching element 131 n. As a result, the value of theestimated load resistance Rn calculated by Expression (7) becomes zero,and it is determined at step 430 that there is an under-resistance. Whenthere is a shorting abnormality at the electrical load 103 n or agrounding abnormality that is contact between the positive side wiring103P and the vehicle body, since the load voltage applied to achieve thetarget current value Isn abruptly decreases, the microprocessor 120Adecreases the energization duty γn. As a result, an abnormal decreaseoccurs in the value of the estimated load resistance Rn calculated byExpression (7), and it is determined at step 430 that there is anunder-resistance.

At step 432 constituting a confirmative determination means, it isdetermined whether the switching element 131 n can be turned off tocheck whether a shorting abnormality has occurred at the switchingelement 131 n. At step 443, a code number for a breakage abnormality ateither the electrical load 103 n or the positive side wiring 103P ornegative side wiring 103N of the electrical load 103 n, a code numberfor a power line shorting abnormality at the positive side wiring 103P,and a code number for a breakage abnormality at the switching element131 n are stored, but it cannot be specified which of the abnormalitieshas occurred.

When there is a breakage abnormality as described above, themicroprocessor 120A increases the energization duty γn in order to allowthe predetermined target current Isn to flow. However, since the loadcurrent Ifn stays in the zero-state instead of being increased howeverthe duty is increased, the estimated load resistance Rn given byExpression (7) becomes too large, and it is determined at step 440 thatthere is an over-resistance. When a power line shorting abnormality atthe positive side wiring 103P is occurred, since the load current Ifn isundetectable, the microprocessor 120A increases the energization duty γnin order to the predetermined target current Isn to flow. Since the loadcurrent Ifn is undetected and kept in the zero-state however the duty isincreased, the estimated load resistance Rn given by Expression (7)becomes too large, and it is determined at step 440 that there is anover-resistance.

Referring to the storage of abnormality history at steps 413, 423, 433a, 433 b, and 443, the history is temporarily stored in the RAM memory122 during the operation of the power supply control unit 100A. When thepower supply switch which is not shown is turned off, the load powersupply relay contact 102 b is immediately turned off, whereas the powersupply switching relay contact 102 a is broken with a delay. The historydata are collectively transferred to the non-volatile data memory 123during this delayed conducting period.

(13) Summaries and Characteristics of Embodiment 1

Embodiment 1 can be summarized and characterized as follows.

As apparent from the above description, the power supply control devicefor on-vehicle electrical loads according to Embodiment 1 of theinvention is a power supply control device comprising a power supplycontrol unit 100A. The power supply control unit 100A includes aplurality of load power supply circuits SPLa to SPLc (hereinafterrepresented by SPLn) for supplying power from a DC driving power supply101 to a plurality of electrical loads 103 a to 103 c (hereinafterrepresented by 103 n), respectively, through switching elements 131 a to131 c (hereinafter represented by 131 n), a plurality of loadcommutation circuits SWLa to SWLc (hereinafter represented by SWLn) forcommutating load currents to the electrical loads 103 n, and a powersupply control circuit PCNTA for supplying energization command outputsDRn to the switching elements 131 n. The load power supply circuitsSPLn, the load commutation circuits SWLn, and the power supply controlcircuit PCNTA are contained in a housing 100 a of the power supplycontrol unit 100A. The power supply control device is characterized asfollows. Commutation diodes 146 a to 146 c (hereinafter represented by146 n) are provided in the load commutation circuits SWLn, respectively,and the commutation diodes 146 n are connected in parallel with therespective electrical loads 103 n to cause currents which have beenflowing through the electrical loads 103 n to flow back when theswitching elements 131 n of the load power supply circuits SPLn areturned off. The commutation diodes 146 n are connected to a vehicle bodyoutside the housing 100 a separately from an internal ground circuitGND2 of the power supply control unit 100A by an external commonnegative line 104. The power supply control circuit PCNTA includes anindividual abnormality detection circuit IADETA, a negative linebreakage abnormality detection circuit 160A, abnormality processingmeans 411, 421, 431, and 441, and abnormality history storing means 413,423, 443, 433 a, and 433 b. The power supply control circuit PCNTAconfigured by using a microprocessor 120A. The microprocessor 120A isconfigured to operate in conjunction with a non-volatile program memory121A in which at least a control program serving as energization commandmeans for the switching elements 131 n is stored, a data memory 123, aRAM memory 122 for arithmetic processes, and a multi-channel A-Dconverter 124. The individual abnormality detection circuit IADETAincludes a plurality of power supply state detection circuits PDETAa toPDETAc (hereinafter represented by PDETAn) for detecting amounts ofpower, specifically, load currents Ifn supplied to the electrical loads103 n and means for determining an individual abnormal state when theamount of power supplied to a certain electrical load among theelectrical loads 103 n deviates from a target amount of supplied power.The individual abnormal state is either breakage or shorting of at leastone of the electrical load, the positive side wiring 103P of theelectrical load, the negative side wiring 103N of the electrical load,and the switching element associated with the electrical load. Thenegative line breakage abnormality detection circuit 160A is a circuitfor determining a breakage abnormality of the external common negativeline 104 by detecting that an electric potential on an anode side ofeach commutation diode 146 n is different from an electric potential atthe internal ground circuit GND2 of the power supply control unit 100A.The abnormality processing means 411, 421, 431, and 441 are means forstopping the energization command output to the switching elements 131 nwhen at least either an individual abnormality or a breakage abnormalityat the external common negative line 104 is detected and for providing anotice of the abnormality. The abnormality history storing means 413,423, 443, 433 a, and 433 b are means for discriminating history ofoccurrence of individual abnormalities and breakage abnormalities at theexternal common negative line 104 in the data memory 123, theabnormalities being discriminated from each other.

In the power supply control device for on-vehicle electrical loads inEmbodiment 1, the commutation diodes 146 n connected in parallel withthe plurality of electrical loads 103 n, respectively, supplied withpower from the DC driving power supply 101 through the respectiveswitching elements 131 n are connected to the vehicle body outside thehousing 100 a of the power supply control unit 100A separately from theinternal ground circuit GND2 of the power supply control unit 100A bythe external common negative line 104. Therefore, neither load currentnor commutation current flows to the internal ground circuit GND2 of thepower supply control unit 100A, which is advantageous in that theelectric potential at the internal ground circuit GND2 can be stabilizedto allow the power supply control circuit PCNTA of the power supplycontrol unit 100A to be operated with stability. Breakage abnormalitiesand shorting abnormalities at the electrical loads 103 n, the positiveside wirings 103P thereof, the negative side wirings 103N thereof, andthe switching elements 131 n are detected by the individual abnormalitydetection circuit IADETA, and breakages at the external common negativeline 104 associated with the commutation diodes 146 n are detected bythe negative line breakage abnormality detection circuit 160A. Measuresare taken against those abnormalities, and the abnormalities areidentified and stored by the abnormality history storing means 413, 423,443, 433 a, and 433 b. Therefore, the efficiency of maintenance andinspection can be advantageously improved by reading history informationat the time of maintenance and inspection.

In Embodiment 1, voltage clamping diodes 1311 are connected to therespective switching elements 131 n to suppress off-voltages thereof.The negative line breakage abnormality detection circuit 160A includes aseries circuit including a constant voltage diode 167 which startsconducting at a voltage lower than the clamping voltage of the voltageclamping diodes 1311, a current limiting resistor 166 connected inseries with the constant voltage diode 167, and a clip diode 168 whoseanode is connected to the internal ground circuit GND2 of the powersupply control unit 100A and a determination element 161 operating inaccordance with the state of energization of the series circuit. Theseries circuit is connected between the internal ground circuit GND2 ofthe power supply control unit 100A and anode terminals A of thecommutation diodes 146 n. The determination element 161 detects abreakage at the external common negative line 104 according to aninduced surge voltage at the electrical load generated when there is abreakage at the external common negative line 104 by detecting anelectric potential at the cathode of the clip diode 168 and supplies analarm signal MNT to the microprocessor 120A. This configuration ischaracterized in that a surge current superimposed on the internalground circuit GND2 of the power supply control unit 100A when there isa breakage at the external common negative line 104 can be suppressed bythe current limiting resistor 166 to a very small value to prevent theapplication of an excessively high surge voltage to the negative linebreakage abnormality detection circuit 160A.

In Embodiment 1, bypass resistors 147 a to 147 c (hereinafterrepresented by 147 n) are connected in parallel with the commutationdiodes 146 n. The negative line breakage abnormality detection circuit160A includes a detection resistor 264 which is supplied with power fromeach of the bypass resistors 147 n through a block diode 263 when thereis a breakage at the external common negative line 104 with theswitching element 131 n in an on-state, and the circuit further includesthe determination element 161. The determination element 161 determinesthat a breakage has occurred at the external common negative line 104based on the fact that the detection resistor 264 has been energized andsupplies an alarm signal MNT to the microprocessor 120A. Thisconfiguration is characterized in that no excessively high surge voltageis applied to the negative line breakage abnormality detection circuit160A because a surge current superimposed on the internal ground circuitGND2 of the power supply control unit 100A when there is a breakage atthe external common negative line 104 is blocked by the block diode 263.

In Embodiment 1, the anode terminals A of the commutation diodes 146 nare connected to the vehicle body outside the housing 100 a through theexternal common negative line 104. A separated ground GND4 connectingthe external common negative line 104 to the vehicle body is separatedfrom at least a unit ground GND1 which connects the internal groundcircuit GND2 of the power supply control unit 100A to the vehicle body.The distance between a load ground GND3 connecting negative terminals ofthe electrical loads 103 n to the vehicle body and the separated groundGND4 is smaller than the distance between the unit ground GND1 and theseparated ground GND4. This configuration is characterized in that thesection of the vehicle body through which a commutation surge currentattributable to a commutation diode 146 n flows can be made short tosuppress electric potential fluctuations at the vehicle body.

In Embodiment 1, the power supply state detection circuits PDETAn havecurrent detecting differential amplifier circuits 150 a to 150 c(hereinafter represented by 150 n), respectively. The current detectingdifferential amplifier circuit 150 n is a circuit for amplifying adifferential voltage across a current detection resistor 141 n connectedbetween a switching element 131 n and an electrical load 103 n with adifferential amplifier 151 n to generate a monitoring voltage Efnproportionate to a load current Ifn at the electrical load 103 n. Anon-inverting input terminal of the differential amplifier 151 n isconnected to a point of connection between the switching element 131 nand the current detection resistor 141 n through first and second seriesresistors 142 n and 152 n. A first negative voltage suppressing diode144 n is connected between a point of connection between the first andsecond series resistors 142 n and 152 n and the internal ground circuitGND2 of the power supply control unit 100A. An inverting input terminalof the differential amplifier 151 n is connected to a point ofconnection between the current detection resistor 141 n and theelectrical load 103 n through third and fourth series resistors 143 nand 153 n. A second negative voltage suppressing diode 145 n isconnected between a point of connection between the third and fourthseries resistors 143 n and 153 n and the internal ground circuit GND2 ofthe power supply control unit 100A. Thus, an excessively high negativevoltage applied to the differential amplifier 151 n when there is abreakage at the external common negative line 104 for the commutationdiodes 146 n is suppressed by the first and second negative voltagesuppressing diodes 144 n and 145 n. This configuration is characterizedin that damage to the differential amplifier 151 n by a surge voltagegenerated by the electrical load 103 n can be prevented when there is abreakage at the external common negative line 104. The configuration isalso characterized in that a surge current superimposed on the internalground circuit GND2 of the power supply control unit 100A when abreakage occurs at the external common negative line 104 can besuppressed to a very small value by the first and third series resistors142 n and 143 n.

In Embodiment 1, the power supply state detection circuits PDETAn haveload voltage monitoring circuits 170 a to 170 c (hereinafter representedby 170 n), respectively. The load voltage monitoring circuit 170 nincludes a comparison/determination logic circuit which compares avoltage proportionate to the load voltage Vfn applied to one resistor174 n of a couple of voltage dividing resistors 173 n and 174 nconnected between a point of connection between the current detectionresistor 141 n and the electrical load 103 n and the internal groundcircuit GND2 of the power supply control unit 100A with a predeterminedthreshold and inputs the result of a determination based on thecomparison to the microprocessor 120A. A clip diode 274 n connected tothe internal ground circuit GND2 at an anode terminal thereof isconnected in parallel with the resistor 174 n of the couple of voltagedividing resistors 173 n and 174 n. The clip diode 274 n suppresses anexcessively high negative voltage applied to the load voltage monitoringcircuit 170 n when there is a breakage at the external common negativeline 104 for the commutation diodes 146 n. This configuration ischaracterized in that damage to the load voltage monitoring circuit 170n attributable to a surge voltage generated by the electrical load 103 ncan be prevented when there is a breakage at the external commonnegative line 104. The configuration is also characterized in that asurge current superimposed on the internal ground circuit GND2 of thepower supply control unit 100A when a breakage abnormality occurs at theexternal common negative line 104 can be suppressed to a very smallvalue by the other resistor 173 n of the couple of voltage dividingresistors 173 n and 174 n.

In Embodiment 1, the microprocessor 120A receives the input of analogsignals which are monitoring voltages Efn supplied from the currentdetecting differential amplifiers 150 n and the input of an analogsignal which is a power supply voltage measurement signal Vd suppliedfrom a power supply voltage measuring circuit 115. Each power supplystate detection circuit PDETAn includes comparison/determinationcircuits 171 n and 271 n forming a load voltage monitoring circuit 170n. The non-volatile program memory 121A includes a control programincluding negative feedback control means 450 which forms theenergization command means. The negative feedback control means 450controls the turning on/off of the switching elements 131 n bygenerating the energization command outputs DRn having variable dutiesγn in accordance with integrated values of deviations betweenenergization target currents Isn for the electrical loads 103 n and loadcurrents Ifn detected by current detecting differential amplifiercircuits 150 n. The power supply voltage measuring circuit 115 includesvoltage dividing resistors 111 and 112 for dividing a driving powersupply voltage Vb provided by the DC driving power supply 101 andinputting the resultant voltage to the microprocessor 120A. A loadvoltage monitoring circuit 170 n includes comparison/determinationcircuits 171 n and 271 n which provide the microprocessor 120A with aninput of a determination made by comparing a voltage proportionate to aload voltage Vfn applied to one resistor 174 n of a couple of voltagedividing resistors 173 n and 174 n connected between a point connectingthe current detection resistor 141 n and the electrical load 103 n andthe internal ground circuit GND2 of the power supply control unit 100Awith a predetermined threshold. This configuration is characterized inthat hardware for negative feedback control can be simplified and inthat a need for analog inputs for monitoring load voltages can beeliminated to provide a compact and inexpensive power supply controldevice.

In Embodiment 1, the power supply control circuit PCNTA includes leakageresistors 149 n having a high resistance connected in parallel with theswitching elements 131 n and load voltage dividing circuits 1410 nprovided on the output side of the switching elements 131 n. Thecomparison/determination circuits include first and secondcomparison/determination circuits 171 n and 271 n for comparing avoltage applied to one resistor 174 n of a couple of voltage dividingresistors 173 n and 174 n of a load voltage monitoring circuit 170 nwith each of first and second threshold voltages proportionate to thedriving power supply voltage Vb. A leakage resistor 149 n supplies sucha very small load current that the electrical load 103 n will not beactivated when the switching element 131 n is off. The respective loadvoltage dividing circuit 1410 n includes a bypass resistor 147 nconnected between a point of connection between the switching element131 n and the current detection resistor 141 n and the anode terminal Aof the commutation diode 146 n. The first threshold voltage isproportionate to a voltage applied to the bypass resistor 147 n throughthe leakage resistor 149 n at the time of occurrence of a breakageabnormality including a breakage at either the electrical load 103 n, orpositive side wiring 103P or negative side wiring 103N of the electricalload 103 n. The second threshold voltage is proportionate to a voltageapplied to the bypass resistor 147 n at the time of occurrence of ashorting abnormality at the switching element 131 n and a power lineshorting that the positive side wiring 103P of the electrical load 103 nis contacted to the power supply line. When a breakage abnormalityoccurs, the output logic of the first comparison/determination circuit171 n is inverted to supply an alarm signal OVn indicating the breakageabnormality to the microprocessor 120A. When either of a shortingabnormality at the switching element 131 n or a power line shortingabnormality at the positive side wiring 103P of the electrical load 103n is occurred, the output logic of the second comparison/determinationcircuit 271 n is inverted to supply an alarm signal SVn indicatingeither of the shorting abnormality at the switching element or powerline shorting abnormality at the positive side wiring to themicroprocessor 120A. This configuration is characterized in thatidentification or determination can be made before energization isstarted with a simple detection circuit on whether there is a breakageabnormality at an electrical load 103 n or a breakage abnormality at thepositive side wiring 103P or negative side wiring 103N thereof orwhether there is a power line shorting abnormality at the positive sidewiring 103P or a shorting abnormality at the switching element 131 n.

In Embodiment 1, the non-volatile program memory 121A includes a controlprogram including load resistance estimation means 408 and at leasteither under-resistance determination means 430 or over-resistancedetermination means 440. The load resistance estimation means 408performs a calculation to estimate a current resistance value Rn of anelectrical load 103 n, which is equivalent to γnVn/Ifn, based on anenergization duty γn of an energization command output DRn output by thenegative feedback control means 450, a driving power supply voltage Vbmeasured by the power supply voltage measuring circuit 115, and a loadcurrent Ifn for the electrical load detected by the current detectingdifferential amplifier circuit 150 n. The under-resistance determinationmeans 430 generates an abnormality determination output when the loadresistance Rn estimated by the load resistance estimation means 408 issmaller than a minimum load resistance Rmin in a low temperatureenvironment, thereby providing a notice of the occurrence of any of ashorting abnormality at the electrical load 103 n, a groundingabnormality that is contact between the positive side wiring 103P andthe vehicle body, and a shorting abnormality at the switching element131 n in the duration of the energization command for the switchingelement 131 n. The over-resistance determination means 440 generates anabnormality determination output when the load resistance Rn estimatedby the load resistance estimation means 408 is greater than a maximumload resistance Rmax in a high temperature environment, therebyproviding a notice of the occurrence of any of a breakage abnormality atthe electrical load 103 n, a breakage abnormality at the positive sidewiring 103P, a breakage abnormality at the negative side wiring 103N, apower line shorting abnormality at the positive side wiring 103P, and abreakage abnormality at the switching element 131 n in the duration ofthe energization command for the switching element 131 n. Thisconfiguration is characterized in that it is possible to detect abnormalstates using inexpensive means without relying on hardware, the abnormalstates including breakage abnormalities at the electrical loads 103 n,power line shorting abnormalities at the positive side wirings 103P,shorting abnormalities at the electrical loads 103 n, groundingabnormalities at the positive side wirings 103P, breakage abnormalitiesat the switching elements 131 n, and shorting abnormalities at theswitching elements 131 n.

In Embodiment 1, the under-resistance determination means 440 furtherincludes a confirmative determination means 432. When theunder-resistance determination means 430 determines that there is astate of under-resistance, the confirmative determination means 432stores the fact that no shorting abnormality has occurred at a switchingelement 131 n as abnormality history information if the load current Ifnhas become zero after the energization command output DRn to theswitching element 131 n was stopped. This configuration is characterizedin that the efficiency of maintenance and inspection operations can beimproved by identifying and storing the cause of the state ofunder-resistance as a grounding abnormality at the positive side wiring103P, a shorting abnormality, a shorting abnormality at the electricalload 103 n or a shorting abnormality at the switching element 131 n.

In Embodiment 1, the abnormality processing means 411, 421, 431, and 441provide an abnormality notice by stopping the energization command to anelectrical load 103 n not only when a breakage abnormality is detectedat the negative line but also when either of a shorting abnormality atthe electrical load 103 n or a grounding abnormality at the positiveside wiring 103P of the electrical load 103 n is detected. Theabnormality history storing means 413, 423, 443, 433 a, and 433 b storesand saves information on shorting abnormalities at the electrical loads103 n and grounding abnormalities at the positive side wirings 103P inthe data memory 123 in addition to the history of occurrence of breakageabnormalities. This configuration is characterized in that comprehensivehistory information can be stored in accordance with the contents ofabnormalities to facilitate maintenance and inspections because anenergization command to an electrical load 103 n is stopped and anabnormality notice is provided not only when there is a breakageabnormality but also when there is a shorting abnormality at theelectrical load 103 n or a grounding abnormality at the positive sidewiring 103P thereof.

Embodiment 2 (21) Configuration of Embodiment 2

FIG. 5 is a general circuit diagram of Embodiment 2 of a power supplycontrol device for on-vehicle electrical loads according to theinvention. The configuration of Embodiment 2 will be described withreference to FIG. 5 with the focus of the description put on differencesfrom the embodiment shown in FIG. 1, and parts identical or equivalentto those in FIG. 1 are indicated by like reference numerals and signs.

In Embodiment 2, as shown in FIG. 5, a power supply control unit 100B isused instead of the power supply unit 101A used in Embodiment 1.Specifically, the power supply control unit 100B constitutes, forexample, a transmission control device for an automobile similarly tothe power supply control unit 101A in Embodiment 1. The power supplycontrol unit 100B is supplied with power from a DC driving power supply101 through a power supply switching relay contact 102 a similarly tothe power supply control unit 100A in Embodiment 1, and it is also fedthrough a load power supply relay contact 102 b. Similarly to the powersupply control unit 101A in Embodiment 1, the power supply control unit100B controls load currents to electrical loads 103 a to 103 c, e.g.,linear solenoids, included in a load circuit 103.

The power supply control unit 100B is contained in a sealed housing 100a. The power supply control unit 100B includes a power supply inputterminals ES1, ES2, and ES3, a unit ground terminal GND, load outputterminals LD1, LD2, and LD3, and three connector terminals LN1, LN2, andLN3. Each of the terminals is disposed in the housing 100 a andelectrically insulated from the housing 100 a. The power supply inputterminals ES1, ES2, and ES3, the unit ground terminal GND, and the loadoutput terminals LD1, LD2, and LD3 are configured similarly to those inEmbodiment 1. The unit ground terminal GND is connected to a vehiclebody at a unit ground GND1 along with an internal ground circuit GND2just as in Embodiment 1.

The connector terminals LN1, LN2, and LN3 of the power supply controlunit 100B are connected to the vehicle body at a separated ground GND4in the vicinity of the connector terminals LN1, LN2, and LN3 throughexternal individual negative lines 104 a, 104 b, and 104 c. Theterminals are connected to a load ground GND3 through the vehicle bodyand connected to negative side wirings 103N of the electrical loads 103a to 103 c. The distance between the separated ground GND4 and the loadground GND3 is smaller than the distance between the separated groundGND4 and the unit ground GND1. As a result, resistance between theseparated ground GND4 and the load ground GND3 is smaller thanresistance between the separated ground GND4 and the unit ground GND1,and fluctuations of an electric potential at the vehicle bodyattributable to commutation at the electrical loads 103 a to 103 c cantherefore be kept small. As indicated by the dotted line in FIG. 5, theexternal individual negative lines 104 a, 104 b, and 104 c may beconnected to the negative side wirings 103N of the electrical loads 103a to 103 c through an external common negative line 104.

The power supply control unit 100B incorporates a power supply controlcircuit PCNTB along with load power supply circuits SPLa to SPLc andload commutation circuits SWLa to SWLc. The power supply control circuitPCNTB is primarily constituted by a microprocessor 120B. The powersupply control circuit PCNTB includes a control power supply circuit110, switching circuits 180 a to 180 c, commutation circuits 1400 a to1400 c, an individual abnormality detection circuit IADETB, and anegative line breakage abnormality detection circuit 160B. Theindividual abnormality detection circuit IADETB detects individualabnormalities at the electrical loads 103 a to 103 c, and the negativeline breakage abnormality detection circuit 160B detects abnormalitiesat the external individual negative lines 104 a to 104 c.

The switching circuits 180 a to 180 c are disposed at the load powersupply circuits SPLa to SPLc, respectively. The switching circuit 180 ais connected in series with the electrical load 103 a to the load powersupply circuit SPLa provided between the power supply input terminal ES1and the load output terminal LD1 to control a load current at theelectrical load 103 a. The switching circuit 180 b is connected inseries with the electrical load 103 b to the load power supply circuitSPLb provided between the power supply input terminal ES1 and the loadoutput terminal LD2 to control a load current at the electrical load 103b. The switching circuit 180 c is connected in series with theelectrical load 103 c to the load power supply circuit SPLc providedbetween the power supply input terminal ES1 and the load output terminalLD3 to control a load current at the electrical load 103 c.

The individual abnormality detection circuit IADETB is constituted bypower supply state detection circuits PDETBa to PDETBc provided inassociation with the electrical loads 103 a to 103 c, respectively, andthe microprocessor 120B. The power supply state detection circuit PDETBaassociated with the electrical load 103 a includes a current detectioncircuit 140 a, a current detecting differential amplifier circuit 150 a,a negative feedback control circuit 190 a, and a load voltage monitoringcircuit 300 a. Similarly, the power supply state detection circuitsPDETBb and PDETBc associated with the electrical loads 103 b and 103 cinclude current detection circuits 140 b and 140 c, current detectingdifferential amplifier circuits 150 b and 150 c, negative feedbackcontrol circuits 190 b and 190 c, and load voltage monitoring circuits300 b and 300 c, respectively.

The commutation circuits 1400 a to 1400 c, the current detectioncircuits 140 a to 140 c, and differential amplifiers 150 a to 150 c forcurrent detection are configured similarly to those in Embodiment 1. Themicroprocessor 120B is used instead of the microprocessor 120A inEmbodiment 1. The switching circuits 180 a to 180 c are used instead ofthe switching circuits 130 a to 130 c in Embodiment 1. The negativefeedback control circuits 190 a to 190 c are additional elementsprovided in Embodiment 2 of the power supply control unit 100B tocontrol the switching circuits 180 a to 180 c. The negative linebreakage abnormality detection circuit 160B is used instead of thenegative line breakage abnormality detection circuit 160A inEmbodiment 1. The load voltage monitoring circuits 300 a to 300 c areused instead of the load voltage monitoring circuits 170 a to 170 c inEmbodiment 1.

The load power supply circuits SPLa to SPLc are formed between the powersupply input terminal ES1 and the load output terminals LD1, LD2, andLD3 in the same way as in Embodiment 1. The load commutation circuitSWLa of the power supply control unit 100B is formed between theconnector terminal LN1 and the load power supply circuit SPLa.Similarly, the load commutation circuits SWLb and SWLc are formedbetween the connector terminals LN2 and LN3 and the load power supplycircuits SPLb and SPLc, respectively. Specifically, the load commutationcircuit SWLa is connected to the connector terminal LN1 at one endthereof and connected to the load power supply circuit SPLa between theswitching circuit 180 a and the current detection circuit 140 a atanother end thereof. Similarly, the load commutation circuits SWLb andSWLc are connected to the connector terminals LN2 and LN3, respectively,at one end thereof. The circuits are also connected to the load powersupply circuit SPLb between the switching circuit 180 b and the currentdetection circuit 140 b and to the load power supply circuit SPLcbetween the switching circuit 180 c and the current detection circuit140 c, respectively, at another end thereof. The commutation circuits1400 a to 1400 c are disposed at the load commutation circuits SWLa toSWLc, respectively.

The microprocessor 120B, which is a major constituent part of the powersupply control circuit PCNTB, is bus-connected to a non-volatile programmemory 121B constituted by, for example, a non-volatile flash memorywhich can be electrically erased at once to allow writing and which canbe read, a RAM memory 122 for arithmetic processes, a data memory 123constituted by a non-volatile EEPROM which can be electrically writtenand read byte by byte, and a multi-channel A-D converter 124. Themicroprocessor is configured for mutual cooperation with those elements.Similarly to the microprocessor 120A in Embodiment 1, the microprocessor120B is supplied with a control power supply voltage Vcc from thecontrol power supply circuit 110. A power supply voltage measuringcircuit 115 is connected to the power supply input terminal ES2connected to the DC driving power supply 101 through the power supplyswitching relay contact 102 a, and a driving power supply voltage Vdmeasured by the same is input to the microprocessor 120B.

The switching circuit 180 a is disposed at the load power supply circuitSPLa and connected in series with the current detection circuit 140 a.Similarly, the switching circuits 180 b and 180 c are disposed at theload power supply circuits SPLb and SPLc, respectively, and connected inseries with the current detection circuits 140 b and 140 c. Theswitching circuits 180 a to 180 c are supplied with power from the DCdriving power supply 101 through the load power supply relay contact 102b and the power supply input terminal ES1. The circuits 180 a to 180 csupply power to the electrical loads 103 a to 103 c associated therewiththrough current detection resistors 141 a to 141 c of the currentdetection circuits 140 a to 140 c and the load output terminals LD1 toLD3, respectively. The switching circuits 180 a to 180 c are turnedon/off under the control of energization command outputs DR1 to DR3generated by the negative feedback control circuits 190 a to 190 c tosupply the electrical loads 103 a to 103 c with load currentsproportionate to energization duties which are ratios of on-times toon/off periods. Details of the switching circuit 180 a will be describedlater with reference to FIG. 6.

Commutation diodes 146 a to 146 c of the commutation circuits 1400 a to1400 c are provided in the load commutation circuits SWLa to SWLc,respectively. The commutation diode 146 a is connected in parallel witha series circuit formed by the current detection resistor 141 a and theelectrical load 103 a. Similarly, the commutation diodes 146 b and 146 care connected in parallel with a series circuit formed by the currentdetection resistor 141 b and the electrical load 103 b and a seriescircuit formed by the current detection resistor 141 c and theelectrical load 103 c, respectively. Anode terminals A of thecommutation diodes 146 a to 146 c are connected to the connectorterminals LN1 to LN3, respectively, and connected to the vehicle bodythrough the external individual negative lines 104 a to 104 c. Thecurrent detecting differential amplifier circuits 150 a to 150 c performdifferential amplification of voltages across the current detectionresistors 141 a to 141 c, respectively to supply monitoring voltages Ef1to Ef3 proportionate to load currents If1 to If3 flowing through theelectrical loads 103 a to 103 c to inputs of the negative feedbackcontrol circuits 190 a to 190 c on one side thereof.

Based on a program serving as a target current command means stored inthe non-volatile program memory 121B, the microprocessor 120B generatesoutputs IT1 to IT3 commanding setting of energization duties α1 to α3proportionate to target current values Is1 to Is3, respectively, andsupplies the setting command outputs IT1 to IT3 to other inputs of thefeedback control circuits 190 a to 190 c. The negative feedback controlcircuit 190 a generates the energization command output DR1 having avariable duty in accordance with an integrated value of a deviationbetween a set voltage Es1 which is proportionate to the target currentvalue Is1 obtained by smoothing the setting command output IT1 and themonitoring voltage Ef1 which is proportionate to the load current valueIf1 detected by the current detecting differential amplifier circuit 150a. The circuit controls the turning on/off of the switching circuit 180a with the energization command output DR1. Similarly, the negativefeedback control circuits 190 b and 190 c generate the energizationcommand outputs DR2 and DR3 having variable duties in accordance withintegrated values of deviations between set voltages Es2 and Es3 whichare proportionate to the target current values Is2 and Is3 obtained bysmoothing the setting command outputs IT2 and Is3, respectively, and themonitoring voltages Ef2 and Ef3 which are proportionate to the loadcurrent values If2 and If3 detected by the current detectingdifferential amplifier circuits 150 b and 150 c. The circuits controlthe turning on/off of the switching circuits 180 b and 180 c with theenergization command outputs DR2 and DR3. Details of the negativefeedback control circuit 190 a will be described later with reference toFIG. 6.

The negative line breakage abnormality detection circuit 160B detects abreakage at the external individual negative lines 104 a to 104 c and abreakage at the negative lines attributable to a contact failure of theconnector terminals LN1, LN2, and LN3 and supplies an alarm signal MNTto the microprocessor 120B. The negative line breakage abnormalitydetection circuit 160B will be described in detail later with referenceto FIG. 7. The load voltage monitoring circuit 300 a monitors a voltageat the load output terminal LD1 to which the positive side wiring 103Pof the electrical load 103 a is connected and supplies a load voltagemeasurement input Vf1, which is an analog signal, to the microprocessor120B. Similarly, the load voltage monitoring circuits 300 b and 300 cmonitor voltages at the load output terminals LD2 and LD3 to which thepositive side wirings 103P of the electrical loads 103 b and 103 c areconnected and supply load voltage measurement inputs Vf2 and Vf3, whichare analog signals, to the microprocessor 120B. Details of the loadvoltage monitoring circuit 300 a will be described later with referenceto FIG. 6.

The switching circuits 180 b and 180 c, the current detection circuits140 b and 140 c, the current detecting differential amplifier circuits150 b and 150 c, the load voltage monitoring circuits 300 b and 300 c,and the negative feedback control circuits 190 b and 190 c associatedwith the electrical loads 103 b and 103 c are configured similarly tothe switching circuit 180 a, the current detection circuit 140 a, thecurrent detecting differential amplifier circuit 150 a, the load voltagemonitoring circuit 300 a, and the negative feedback control circuit 190a associated with the electrical load 103 a, respectively. Themicroprocessor 120B generates the setting command outputs IT1 to IT3 andoperates on the load voltage measurement inputs Vf1 to Vf3 and the powersupply voltage measurement input Vd as analog inputs.

FIG. 6 is a detailed circuit diagram of a major part of Embodiment 2shown in FIG. 5. FIG. 6 shows the microprocessor 120B constituting thepower supply control circuit PCNTB along with the switching circuit 180a, the current detection circuit 140 a, the commutation circuit 1400 a,the negative feedback control circuit 190 a, the differential amplifier150 a for current detection, and load voltage monitoring circuit 300 aassociated with the electrical load 103 a. The description will be madewith reference to FIG. 6 and will be focused on differences from what isshown in FIG. 2. The switching circuits 180 b and 180 c, the currentdetection circuits 140 b and 140 c, the commutation circuits 1400 b and1400 c, the negative feedback control circuits 190 b and 190 c, thedifferential amplifiers 150 b and 150 c for current detection, and loadvoltage monitoring circuits 300 b and 300 c associated with theelectrical loads 103 b and 103 c are configured similarly to theswitching circuit 180 a, the current detection circuit 140 a, thecommutation circuit 1400 a, the negative feedback control circuit 190 a,the differential amplifier 150 a for current detection, and load voltagemonitoring circuit 300 a associated with the electrical load 103 a,respectively.

Referring to FIG. 6, the switching circuit 180 a comprises the switchingelement 181 a as a primary element. The switching circuit 180 a includesthe switching element 181 a, various resistors 185 a, 186 a, and 189 a,a voltage clamping diode 184 d, an NPN transistor 187 a, and a blockdiode 188 a. The switching element 181 a is a power transistor,specifically, a PNP type bipolar transistor. The driving power supplyvoltage Vb is applied to an emitter terminal E of the switching element181 a, and a collector terminal C of the element is connected to theload output terminal LD1 through the current detection resistor 141 a. Abase terminal B of the switching element 181 a is connected to thecollector terminal C through the voltage clamping diode 184 a, and astabilizing resistor 185 a for an off-state of the switching element 181a is connected between the emitter terminal E and the base terminal B.

The base terminal B of the switching element 181 a is connected to acollector terminal C of the NPN transistor 187 a through the baseresistor 186 a, and en emitter terminal E of the NPN transistor 187 a isconnected to the internal ground circuit GND2 of the power supplycontrol unit 100B through the block diode 188 a. A cathode terminal K ofthe block diode 188 a is connected to the internal ground circuit GND2,and an anode terminal A of the same is connected to an emitter terminalE of the NPN transistor 187 a. The energization command output DR1 issupplied from the negative feedback control circuit 190 a to a baseterminal B of the NPN transistor 187 a through the driving resistor 189a, and the NPN transistor 187 a and the switching element 181 a areturned on when the logical level of the energization command output DR1becomes “H”. The commutation circuit 1400 a is similar to that inEmbodiment 1, and it has a commutation diode 146 a and a bypass resistor147 a. The bypass resistor 147 a forms a load voltage dividing circuit1410 a in combination with a leakage resistor 149 a connected betweenthe emitter terminal E and the collector terminal C of the switchingelement 181 a. The load voltage dividing circuit 1410 a has the samefunction as that of the load voltage dividing circuit 1410 a shown inFIG. 2.

The current detection circuit 140 a and the current detectingdifferential amplifier circuit 150 a are configured similarly to thosein FIG. 2, but the monitoring voltage Ef1 proportionate to the loadcurrent If1 detected by the current detecting differential amplifiercircuit 150 a is input to the negative feedback control circuit 190 a.The negative feedback control circuit 190 a includes a smoothing circuit191 a and a deviation integrating circuit 192 a. The smoothing circuit191 a smoothes the setting command output IT1 from the microprocessor120B to generate a set voltage Es1 proportionate to a target currentvalue Is1. The set voltage Es1 from the smoothing circuit 191 a and themonitoring voltage Ef1 proportionate to the load current If1 detected bythe current detecting differential amplifier circuit 150 a are input tothe deviation integrating circuit 192 a. The deviation integratingcircuit 192 a generates an energization command output DR1 having avariable duty γ1 in accordance with an integrated value of a deviationbetween the set voltage Es1 and the monitoring voltage Ef1 to controlthe turning on/off of the switching element 181 a.

The load voltage monitoring circuit 300 a includes voltage dividingresistors 301 a and 302 a connected between the load output terminal LD1and the internal ground circuit GND2 and a clip diode 305 a connected inparallel with the resistor 302 a. An anode terminal of the clip diode305 a is connected to the internal ground circuit GND2, and a cathodeterminal K of the diode is connected to a point of connection betweenthe voltage dividing resistors 301 a and 302 a. The load voltagemonitoring circuit 300 a further includes an integration resistor 303 aand a smoothing capacitor 304 a forming a smoothing circuit. A voltageacross the voltage dividing resistor 302 a is smoothed by theintegration resistor 303 a and the smoothing capacitor 304 a and inputto the microprocessor 120B, whereby a load voltage measurement input Vf1proportionate to the load voltage is supplied as an analog signal.

FIG. 7 shows the negative line breakage abnormality detection circuit160B of Embodiment 2. The negative line breakage abnormality detectioncircuit 160B will be described with reference to FIG. 7 with the focusof the description put on differences from the circuit shown in FIG. 3.Referring to FIG. 7, the negative line breakage abnormality detectioncircuit 160B includes a determination element 161 constituted by a PNPtransistor which is supplied with the control power supply voltage Vcc,a collector resistor 162, an output resistor 163 a, an integratingcapacitor 163 b and a stabilizing resistor 164 for an off-state of thedetermination element 161. The circuit supplied an alarm signal MNT tothe microprocessor 120B.

A series circuit formed by a driving resistor 261 and a drivingtransistor 262 is connected to a base circuit of the determinationelement 161. A series circuit formed by a combined block diode 269 and adetection resistor 264 is connected to a base circuit of the drivingtransistor 262. A stabilizing transistor 265 for an off state of thedriving transistor 262 is connected between a base terminal B and anemitter terminal E of the driving transistor 262.

When there is a breakage at the external individual negative lines 104 ato 104 c connected to the connector terminals LN1, LN2, and LN3 with anyof the switching elements 181 a to 181 c in the on-state, the transistor262 is energized and driven through any of the bypass resistors 147 a to147 c and the detection resistor 264, and the determination element 161is thereby turned on to change the logical level of the alarm signal MNTto “H”.

Thus, the determination element 161 generates an alarm signal MNT bydetecting a positive electric potential generated at the anode terminalsA of the commutation diodes 146 a to 146 c by the bypass resistors 147 ato 147 c during a period in which the switching elements 181 a to 181 care on. When the connector terminals LN1, LN2, and LN3 are properlyconnected to the vehicle body by the external individual negative lines104 a to 104 c, no electric potential is generated at the anodeterminals A of the commutation diodes 146 a to 146 c, and the logicallevel of the alarm signal generated by the determination element 161 istherefore “L” which indicates a normal state. The external individualnegative lines 104 a to 104 c may be bundled together outside the powersupply control unit 100B and connected to the vehicle body in theposition of the load ground GND3 as a single common negative line.

(22) Effects and Operations of Embodiment 2

Effects and operations of Embodiment 2 of the invention shown in FIGS. 5to 7 will now be described. Referring to FIG. 5, when a power supplyswitch which is not shown is turned on, the power supply switching relaycontact 102 a is turned on to apply the driving power supply voltage Vbto the control power supply circuit 110, and the control power supplycircuit 110 generates the control power supply voltage Vcc and suppliesit to the microprocessor 120B. When the microprocessor 120B startsoperating, the load power supply relay contact 102 b is turned on by anenergization circuit which is not shown. Based on an operation controlprogram stored in the non-volatile program memory 121B, themicroprocessor 120B determines which of the plurality of electricalloads 103 a to 103 c is to be supplied with a load current anddetermines the amount of the load current. The microprocessor thereaftergenerates the setting command outputs IT1 to IT3 which are pulse outputsof the energization duties α1 to α3 proportionate to the target loadcurrent values Is1 to Is3 based on a control program to serve as atarget current command means stored in the non-volatile program memory121B.

The negative feedback control circuit 190 a controls the turning on/offof the switching element 181 a by generating the energization commandoutput DR1 having a variable duty γ1 in accordance with an integratedvalue of a deviation between the set voltage Es1 which is proportionateto the target load current value Is1 for the electrical load 103 aobtained by smoothing the setting command output IT1 and the monitoringvoltage Ef1 which is proportionate to the load current If1 detected bythe current detecting differential amplifier circuit 150 a. When theswitching element 181 a is on, the load current If1 flows from thepositive terminal of the DC driving power supply 101 and circulatesthrough a path formed by the load power supply relay contact 102 b, thepower supply input terminal ES1, the switching element 181 a, thecurrent detection resistor 141 a, the positive side wiring 103P, theelectrical load 103 a, the negative side wiring 103N, the load groundGND3, the vehicle body, and a power supply ground GND0 back to thenegative terminal of the DC driving power supply 101. No load currentflows to the internal ground circuit GND2 of the power supply controlunit 100B at all. When the switching elements 181 b and 181 c are turnedon, the load currents If2 and If3 flowing through the electrical loads103 b and 103 c follow similar paths, and no load current flows to theinternal ground circuit GND2 of the power supply control unit 100B atall.

When the switching element 181 a is turned off, the load current If1flows from the negative terminal of the electrical load 103 a andcirculates through a path formed by the negative side wiring 103N, theload ground GND3, the vehicle body, the separated ground GND4, theexternal individual negative line 104 a, the connector terminal LN1, thecommutation diode 146 a, the current detection resistor 141 a, the loadoutput terminal LD1, and the positive side wiring 103P back to thepositive terminal of the electrical load 103 a. In this case again, noload current flows to the internal ground circuit GND2 of the powersupply control unit 100B at all. When the switching elements 181 b and181 c are turned off, the load currents If2 and If3 commutated from theelectrical loads 103 b and 103 c follow similar paths, and no loadcurrent flows to the internal ground circuit GND2 of the power supplycontrol unit 100B at all.

Let us now assume that the external individual negative lines 104 a to104 c are not provided and that the anode terminal A of the commutationdiode 146 a is connected to the internal ground circuit GND2 of thepower supply control unit 100B. In this case, when the switching element181 a is turned off, the load current If1 flows from the negativeterminal of the electrical load 103 a and circulates through a pathformed by the negative side wiring 103N, the load ground GND3, the unitground GND1 of the power supply control unit 100B, the unit groundterminal GND, the internal ground circuit GND2, the commutation diode146 a, the current detection resistor 141 a, the load output terminalLD1, and the positive side wiring 103P back to the positive terminal ofthe electrical load 103 a. A problem arises in that a commutation surgecurrent flows into the internal ground circuit GND2 of the power supplycontrol unit 100B to cause fluctuations of the electric potential at theinternal ground circuit GND2.

In Embodiment 2, the anode terminals A of the commutation diodes 146 ato 146 c are connected to the vehicle body at the separated ground GND4outside the power supply control unit 100B through the externalindividual negative lines 104 a to 104 c, which makes it possible toprevent the load currents If1, If2, and If3 from flowing into theinternal ground circuit GND2 of the power supply control unit 100B. Onthe contrary, when there is a contact failure at the connector terminalsLN1, LN2, and LN3 or a breakage abnormality at the external individualnegative lines 104 a to 104 c, the commutating function of thecommutation diodes 146 a to 146 c is deteriorated, which results inanother problem in that an induced surge voltage is generated byinductive components of the electrical loads 103 a, 103 b, and 103 cwhen the switching elements 181 a to 181 c are turned off.

The surge voltage is suppressed to, for example, about 50 volts by thevoltage clamping diodes 184 a for suppressing an off-voltage provided atthe switching elements 181 a to 181 c. However, the suppressed surgevoltage will be applied to all circuits in the power supply controlcircuit PCNTB of the power supply control unit 100B which are connectedbetween the internal ground circuit GND2 and the load output terminalsLD1, LD2, and LD3.

Referring to FIG. 6, the block diode 188 a associated with the switchingelement 181 a blocks a countercurrent attributable to the suppressedsurge voltage. First and second negative voltage suppressing diodes 144a and 145 a of the current detection circuit 140 a suppress inputelectric potentials of a differential amplifier 151 a to negativeelectric potentials of, for example, about 1 volt that is the forwardvoltage of the first and second negative voltage suppressing diodes 144a and 145 a. The first and third series resistors 142 a and 143 asuppress a surge current which circulates from the unit ground GND1 tothe load output terminal LD1 via the internal ground circuit GND2 andthe first or second negative voltage suppressing diode 144 a or 145 a,thereby suppressing fluctuations of the electric potential at theinternal ground circuit GND2.

Similarly, the clip diode 305 a of the load voltage monitoring circuit300 a suppresses the input electric potential of the voltage dividingresistor 302 a to a negative electric potential of, for example, about 1volt that is the forward voltage of the clip diode 305 a. The voltagedividing resistor 301 a suppresses a surge current which circulates fromthe unit ground GND1 to the load output terminal LD1 via the internalground circuit GND2 and the clip diode 305 a, thereby suppressingfluctuations of the electric potential at the internal ground circuitGND2. Effects and operations of the switching elements 181 b and 181 c,the current detection circuits 141 b and 141 c, and the load voltagemonitoring circuits 300 b and 300 c associated with the electrical loads103 b and 103 c are similar to the effects and operations of theswitching element 181 a, the current detection circuit 141 a, and theload voltage monitoring circuit 300 a associated with the electricalload 103 a.

Referring to FIG. 7, the combined block diode 269 of the negative linebreakage abnormality detection circuit 160B prevents a commutation surgecurrent from flowing from the detection resistor 264 to the load outputterminals LD1 to LD3. However, when the switching elements 181 a to 181c are on, the transistor 262 is turned on by the bypass resistors 147 ato 147 c, the combined block diode 269, and the detection resistor 264,and the determination element 161 is consequently turned on.

The external common negative line 104 is used in Embodiment 1 as shownin FIG. 3. In Embodiment 2, the external individual negative lines 104 ato 104 c are used as shown in FIG. 7, and the connector terminals LN1 toLN3 associated with the external individual negative lines 104 a to 104c are used instead of the common terminal COM shown in FIG. 3. Thus, noconcentration of currents commutated from the electrical loads 103 a to103 c occurs at the connector terminals LN1 to LN3, and it is thereforepossible to prevent an over-current from flowing to the connectorterminals LN1 to LN3. Although it is desirable to extend the externalindividual negative lines 104 a to 104 c to the position of the loadground GND3, they are connected to the vehicle body in the position ofthe separated ground GND4 provided in the vicinity of the connectorterminals LN1 to LN3 in order to keep the number of wirings small.

FIG. 8 is a flow chart for explaining operations of Embodiment 2. Theoperations of Embodiment 2 will now be described with reference to FIG.8. In FIG. 8, step 800 is a step at which load current control forming apart of various control flows of the microprocessor 120B is started. Thesubsequent step 801 is a step which constitutes a negative line breakageabnormality detection means. At step 801, the state of input of thealarm signal MNT is monitored to determine the negative line breakageabnormality detection circuit 160B has detected any breakage abnormalityat the negative lines. When a breakage abnormality has occurred at thenegative lines and the result of the determination at step 801 istherefore YES, the process proceeds to step 811. If the result of thedetermination at step 801 is NO, the process proceeds to step 802.

Step 811 is a step which constitutes an abnormality processing meansand, more specifically, an all output stopping means and an abnormalitynotification means. At step 811, all of the setting command outputs IT1,IT2, and IT3 are stopped, and an alarm output ER is generated toactivate an alarm indicator 105. The subsequent step 813 is a step whichconstitutes an abnormality history storing means and at which theinformation of the occurrence of a breakage abnormality at the negativelines is written and stored in a data memory 123. The subsequent step860 is a current control operation ending step. At step 860, themicroprocessor 120B executes control operations other than currentcontrol, and the operation starting step 800 is activated again after apredetermined time passes to repeat the series of control operations.

Step 802 is a step which constitutes a load number setting/updatingmeans. At step 802, load numbers n (n=a, b, c, and so on) for aplurality of electrical loads 103 a, 103 b, 103 c, and so on arespecified and sequentially updated and specified. The subsequent step803 is a step which constitutes a target current value reading means. Atstep 803, a target current value Isn associated with an electrical load103 n having a load number n specified at step 802 is read. The targetcurrent value Isn is determined based on another control program whichis not shown. The subsequent step 804 is a step which constitutes a loadvoltage reading means. At step 804, a load voltage value Vfn of theelectrical load 103 n detected by a load voltage monitoring circuit 300n is read. The subsequent step 805 is a step which constitutes aninitial operation determination means. At step 805, it is determinedwhether an initial operation is being performed based on a determinationmade at a subsequent step 807 on whether an initialization complete flaghas been set. When an initial operation is being performed and theresult of the determination at step 805 is therefore YES, the processproceeds to step 806. If the result of the determination at step 805 isNO, the process proceeds to step 850.

Step 806 is a step which constitutes an initial check starting means. Atstep 806, an energization duty γn of a setting command output ITnassociated with the electrical load 103 n specified at step 802 isnullified to perform an initial check. The subsequent step 820 a is astep which constitutes a second comparison/determination means. At step820 a, it is determined whether the load voltage value Vfn read at step804 is in an abnormal state in which it is equal to or higher than asecond threshold voltage value V2. When the voltage is in the abnormalstate and the result of the determination at step 820 a is thereforeYES, the process proceeds to step 821. If the result of thedetermination at step 820 a is NO, the process proceeds to step 820 b.The second threshold voltage value V2 is given by Expression (8) shownbelow where Vb represents the driving power supply voltage and R301 nand R302 n represent resistances of voltage dividing resistors 301 n and302 n of the load voltage monitoring circuit 300 n associated with theelectrical load 103 n.

V2=Vb×R302n/(R301n+R302n)  (8)

Step 820 b is a step which constitutes a first comparison/determinationmeans. At step 820 b, it is determined whether the load voltage valueVfn read at step 804 is in an abnormal state in which it is equal to orhigher than a first threshold voltage value V1. When the voltage is inthe abnormal state and the result of the determination at step 820 b istherefore YES, the process proceeds to step 821. If the result of thedetermination at step 820 b is NO, the process proceeds to step 807. Thefirst threshold voltage value V1 is given by Expression (9) shown belowwhere R149 n represents the resistance of a leakage resistor 149 nconnected between an emitter terminal E and a collector terminal C ofthe switching element 181 n and R147 n represents the resistance of abypass resistor 147 n.

V1=V2×R147n/(R149n+R147n)  (9)

Step 821 is a step which constitutes an abnormality processing means,more specifically, a relevant output stopping means and an abnormalitynotification means. At step 821, the relevant setting command output ITnis stopped, and an alarm output ER is generated to activate the alarmindicator 105. The subsequent step 823 is a step which constitutes anabnormality history storing means, more specifically, a categorizedabnormality history storing means. At step 823, the information of theoccurrence of an abnormality associated with the second thresholdvoltage value V2 or the first threshold voltage value V1 is written andstored in the data memory 123. At this step 823, when an abnormality isdetermined at step 820 a, a shorting abnormality at the switchingelement 181 n or a power line shorting abnormality of the positive sidewiring 103P with respect to the electrical load 103 n is stored. When noabnormality is determined at step 820 a but an abnormality is determinedat step 820 b, a breakage abnormality at any of the electrical load 103n, the positive side wiring 103P, and the negative side wiring 103N isstored. Step 823 is followed by current control operation ending step860.

Step 807 is a step at which an initialization complete flag is set andwhich is followed by step 850. The initialization complete flag set atstep 807 is reset when the target current value Isn read at step 803 iszero. The result of the determination at step 805 will be YES if theinitialization complete flag has been reset. Step 850 is a step whichconstitutes a target current command means. At step 850, a settingcommand output ITn having an energization duty an proportionate to thetarget current value Isn read at step 803 is generated. The subsequentstep 808 is a step which constitutes a load resistance estimation means.At step 808, a load resistance Rn is calculated by Expression (10) shownbelow based on the current load voltage value Vfn read at step 804 andthe target current value Isn read at step 803, and the step is followedby step 830.

Rn=Vfn/Isn  (10)

Step 830 is a step which constitutes an over-resistance determinationmeans. At step 830, it is determined whether the load resistance Rncalculated at step 808 is an abnormal value which is greater than amaximum resistance Rmax of the electrical load 103 n at hightemperatures. When the result of the determination at step 830 is YES,the process proceeds to step 831. If the result of the determination atstep 830 is NO, the process proceeds to step 840. Step 831 is a stepwhich constitutes an abnormality processing means, more specifically, arelevant output stopping means and an abnormality notification means. Atstep 831, the relevant setting command output ITn is stopped, and thealarm output ER is generated to activate the alarm indicator 105. Thesubsequent step 832 is a step which constitutes a confirmativedetermination means. At step 832, it is determined whether the loadvoltage Vfn has become zero as a result of the stoppage of the settingcommand output ITn at step 831. When the load voltage Vfn has beenproperly restored to zero and the result of the determination at step832 is therefore YES, the process proceeds to step 833 b. If the resultof the determination at step 832 is NO, the process proceeds to step 833a.

Steps 833 a and 833 b are steps which constitute an abnormality historystoring means, more specifically, a categorized abnormality historystoring means. At steps 833 a and 833 b, abnormality information basedon the result of the confirmative determination at step 832 is writtenand stored in the data memory 123 when an over-resistance is determinedat step 830. At step 833 a, the occurrence of a shorting abnormality atthe switching element 181 n in the duration of an energization commandto the switching element 181 n is recorded as abnormality historyinformation. Abnormality history information recorded at step 833 b isthe occurrence of any of a breakage abnormality at the electrical load103 n, a breakage abnormality at the positive side wiring 103P, abreakage abnormality at the negative side wiring 103N, and a power lineshorting abnormality that the positive side wiring 103P is contacted tothe power supply line connected to the positive terminal of the DCdriving power supply 101 in the duration of an energization command forthe switching element 181 n. The abnormality history information alsoincludes the fact that no shorting abnormality has occurred at theswitching element 181 n. Steps 833 a and 833 b are followed by currentcontrol operation ending step 860.

Step 840 is a step which constitutes an under-resistance determinationmeans. At step 840, it is determined whether the load resistance Rncalculated at step 808 is an abnormal value which is smaller than aminimum resistance Rmin of the electrical load 103 n at lowtemperatures. When the result of the determination at step 840 is YES,the process proceeds to step 841. If the result of the determination atstep 840 is NO, the process proceeds to step 860. Step 841 is a stepwhich constitutes an abnormality processing means, more specifically, arelevant output stopping means and an abnormality notification means. Atstep 841, the relevant setting command output ITn is stopped, and thealarm output ER is generated to activate the alarm indicator 105. Thesubsequent step 843 is a step which constitutes an abnormality historystoring means, more specifically, a categorized abnormality historystoring means. At step 843, information of the occurrence of anunder-resistance abnormality detected at step 840 is written and storedin the data memory 123. The occurrence of an under-resistanceabnormality means that a shorting abnormality at the electrical load 103n, a grounding abnormality that is contact between the positive sidewiring 103P and the vehicle body, and a breakage abnormality at theswitching element 181 n has occurred in the duration of an energizationcommand to the switching element 181 n. The occurrence of thoseabnormalities is stored in the data memory 123. Step 843 is followed bycurrent control operation ending step 860. At this current controloperation ending step 860, the microprocessor 120B executes controloperations other than current control. Operation starting step 800 isactivated again after a predetermined time passes to repeat the seriesof control operations.

The control flow will now be summarized. Step 801 is a step formonitoring the state of input of the alarm signal MNT to determinewhether any negative breakage abnormality has been detected by thenegative line breakage abnormality detection circuit 160B. The negativeline breakage abnormality detection circuit 160B is enabled forabnormality detection when at least one of the plurality of electricalloads 103 a to 103 c is conducting. At step 813, a code number for abreakage abnormality at the negative line is stored, but no electricalload is specified. At steps 820 a and 820 b, the load voltage value Vfnmeasured by the load voltage monitoring circuit 300 n is compared withthe first and second threshold voltage values V1 and V2. At step 823, acode number for a shorting abnormality at the switching element 181 nand a code number for the power line shorting abnormality at thepositive side wiring 103P of the electrical load 103 n are stored whenthe occurrence of an abnormality has been determined at step 820 a, butit can not be specified which of the abnormalities has occurred. At step823, a code number for a breakage abnormality at the electrical load 103n or a code number for a breakage at either the positive side wiring103P or negative side wiring 103N of the electrical load 103 n is storedwhen no abnormality has been determined at step 820 a whereas theoccurrence of an abnormality has been determined at step 820 b. However,the position of the breakage cannot be identified.

Steps 830 and 840 execute abnormality determination using software bymonitoring the resistance of the electrical load 103 n. Anyover-resistance or under-resistance is determined at steps 830 and 840when the setting command output is generated. A code number for ashorting abnormality at the switching element 181 n is stored at step833 a. At step 833 b, a code number for a shorting abnormality at theelectrical load 103 n and a code number for a power line shortingabnormality at the positive side wiring 103P of the electrical load 103n are stored, but it cannot be specified which of a load breakage and apower line showing abnormality has occurred.

When there is a shorting abnormality which disallows the switchingelement 181 n to be turned off, a voltage higher than the load voltageaccording to the target current value ISn is applied to the electricalload 103 n. Although the negative feedback control circuit 190 ndecreases the energization duty γn in order to obtain a current closerto the target current value Isn, the load voltage Vfn stays at themaximum value instead of being decreased however the energization dutyγn is decreased because of the shorting at the switching element 181 n.As a result, the value of the estimated load resistance Rn calculated byExpression (10) becomes excessively large, and it is determined at step830 that there is an over-resistance. When there is a breakageabnormality at the electrical load 103 n or a power line shortingabnormality at the positive side wiring 103P, since the load current Ifndetected by the differential amplifier 150 n for current detectionabruptly decreases, the negative feedback control circuit 190 ncontinues to increase the energization duty γn. As a result, the loadvoltage to achieve the target current value Isn is maximized to cause anabnormal increase occurs in the value of the estimated load resistanceRn calculated by Expression (10), and it is determined at step 830 thatthere is an over-resistance.

At step 832 constituting a confirmative determination means, it isdetermined whether the switching element 181 n can be turned off tocheck whether a shorting abnormality has occurred at the switchingelement 181 n. At step 843, code numbers for a shorting abnormality atthe electrical load 103 n, a grounding abnormality at the positive sidewiring 103P of the electrical load 103 n, and a breakage abnormality atthe switching element 181 n are stored, but it cannot be specified whichof those abnormalities has occurred. When a shorting abnormality at theelectrical load 103 n, a grounding abnormality at the positive sidewiring 103P, or a breakage abnormality at the switching element 181 noccurs, the load voltage measured by the load voltage monitoring circuit300 n becomes zero, and the estimated load resistance Rn given byExpression (10) becomes excessively small. It is therefore determined atstep 840 that there is an under-resistance. Referring to the storage ofabnormality history at steps 813, 823, 833 a, 833 b, and 843, thehistory is temporarily stored in the RAM memory 122 during the operationof the power supply control unit 100B. When the power supply switchwhich is not shown is turned off, the load power supply relay contact102 b is immediately turned off, whereas the power supply switchingrelay contact 102 a is broken with a delay. The history data arecollectively transferred to the non-volatile data memory 123 during thisdelayed conducting period.

(23) Summaries and Characteristics of Embodiment 2

Embodiment 2 can be summarized and characterized as follows.

As apparent from the above description, the power supply control devicefor on-vehicle electrical loads according to Embodiment 2 of theinvention is a power supply control device comprising a power supplycontrol unit 100B. The power supply control unit 100B includes aplurality of load power supply circuits SPLa to SPLc (hereinafterrepresented by SPLn) for supplying power from a DC driving power supply101 to a plurality of electrical loads 103 a to 103 c (hereinafterrepresented by 103 n), respectively, through switching elements 181 a to181 c (hereinafter represented by 181 n), a plurality of loadcommutation circuits SWLa to SWLc (hereinafter represented by SWLn) forcommutating load currents to the electrical loads 103 n, and a powersupply control circuit PCNTB for supplying energization command outputsDRn to the switching elements (181 n). The load power supply circuitsSPLn, the load commutation circuits SWLn, and the power supply controlcircuit PCNTB are contained in a housing 100 a of the power supplycontrol unit 100B. Commutation diodes 146 a to 146 c (hereinafterrepresented by 146 n) are provided in the load commutation circuitsSWLn, respectively, and the commutation diodes 146 n are connected inparallel with the respective electrical loads 103 n to cause currentswhich have been flowing through the electrical loads 103 n to flow backwhen the switching elements 181 n of the load power supply circuits SPLnare turned off. The commutation diodes 146 n are connected to a vehiclebody outside the housing 100 a separately from an internal groundcircuit GND2 of the power supply control unit 100B by externalindividual negative lines 104 a to 104 c (hereinafter represented by 104n) constituting an external negative line. The power supply controlcircuit PCNTB includes an individual abnormality detection circuitIADETB, a negative line breakage abnormality detection circuit 160B,abnormality processing means 811, 821, 831, and 841, and abnormalityhistory storing means 813, 823, 843, 833 a, and 833 b. The power supplycontrol circuit PCNTB is configured by using a microprocessor 120B. Themicroprocessor 120B is configured to operate in conjunction with anon-volatile program memory 121B in which at least a control programserving as energization command means for the switching elements 181 nis stored, a data memory 123, a RAM memory 122 for arithmetic processes,and a multi-channel A-D converter 124. The individual abnormalitydetection circuit IADETB includes a plurality of power supply statedetection circuits PDETBa to PDETBc (hereinafter represented by PDETBn)for detecting amounts of power, specifically, load currents Ifn suppliedto the electrical loads 103 n and means for determining an individualabnormal state when the amount of power supplied to a certain electricalload among the electrical loads 103 n deviates from a target amount ofsupplied power. The individual abnormal state is either breakage orshorting of at least one of the electrical load, the positive sidewiring 103P of the electrical load, the negative side wiring 103N of theelectrical load, and the switching element associated with theelectrical load. The negative line breakage abnormality detectioncircuit 160B is a circuit for determining a line breakage abnormality atthe external individual negative lines 104 n by detecting that anelectric potential on an anode side of each commutation diode 146 n isdifferent from an electric potential at the internal ground circuit GND2of the power supply control unit 100B. The abnormality processing means811, 821, 831, and 841 are means for stopping the energization commandoutput to the switching elements when at least either an individualabnormality or a breakage abnormality at the external individualnegative lines 104 n is detected and for providing a notice of theabnormality. The abnormality history storing means 813, 823, 843, 833 a,and 833 b are means for storing and saving the history of occurrence ofindividual abnormalities and breakage abnormalities at the externalindividual negative line 104 n in the data memory 123 withidentification of the abnormalities.

In the power supply control device for on-vehicle electrical loads inEmbodiment 2, the commutation diodes 146 n connected in parallel withthe plurality of electrical loads 103 n, respectively, supplied withpower from the DC driving power supply 101 through the respectiveswitching elements 181 n are connected to the vehicle body outside thehousing 100 a of the power supply control unit 100B separately from theinternal ground circuit GND2 of the power supply control unit 100B bythe external individual negative lines 104 n. Therefore, neither loadcurrent nor commutation current flows to the internal ground circuit GNDof the power supply control unit 100B, which is advantageous in that theelectric potential at the internal ground circuit GND2 can be stabilizedto allow the power supply control circuit PCNTB of the power supplycontrol unit 100B to be operated with stability. Breakage abnormalitiesand shorting abnormalities at the electrical loads 103 n, the positiveside wirings 103P thereof, the negative side wirings 103N thereof, andthe switching elements 181 n are detected by the individual abnormalitydetection circuit IADETB, and breakages at the external individualnegative lines 104 n associated with the commutation diodes 146 n aredetected by the negative line breakage abnormality detection circuit160B. Measures are taken against those abnormalities, and theabnormalities are identified and stored by the abnormality historystoring means 813, 823, 843, 833 a, and 833 b. Therefore, the efficiencyof maintenance and inspection can be advantageously improved by readinghistory information at the time of maintenance and inspection.

In Embodiment 2, bypass resistors 147 a to 147 c (hereinafterrepresented by 147 n) are connected in parallel with the commutationdiodes 146 n. The negative line breakage abnormality detection circuit160B includes a detection resistor 264 which is supplied with power fromeach of a bypass resistor 147 n through a combined block diode 269 whenthere is a breakage at the external individual negative lines 104 n withthe switching element 181 n in an on-state, and the circuit furtherincludes the determination element 161. The determination element 161determines that a breakage has occurred at the external individualnegative lines 104 n based on the fact that the detection resistor 264has been energized and supplies an alarm signal MNT to themicroprocessor 120B. This configuration is characterized in that noexcessively high surge voltage is applied to the negative line breakageabnormality detection circuit 160B because a surge current superimposedon the internal ground circuit GND2 of the power supply control unit100B when there is a breakage at the external individual negative lines104 n is blocked by the combined block diode 269.

In Embodiment 2, the anode terminals A of the commutation diodes 146 nare connected to the vehicle body outside the housing 100 a through theexternal individual negative lines 104 n. A separated ground GND4connecting the external individual negative lines 104 n to the vehiclebody is separated from at least a unit ground GND1 which connects theinternal ground circuit GND2 of the power supply control unit 100B tothe vehicle body. The distance between a load ground GND3 connectingnegative terminals of the electrical loads 103 n to the vehicle body andthe separated ground GND4 is smaller than the distance between the unitground GND1 and the separated ground GND4. This configuration ischaracterized in that the section of the vehicle body through which acommutation surge current attributable to a commutation diode 146 nflows can be made short to suppress electric potential fluctuations atthe vehicle body.

In Embodiment 2, the power supply state detection circuits PDETBn havecurrent detecting differential amplifier circuits 150 a to 150 c(hereinafter represented by 150 n), respectively. A current detectingdifferential amplifier circuit 150 n is a circuit for amplifying adifferential voltage across a current detection resistor 141 n connectedbetween a switching element 181 n and an electrical load 103 n with adifferential amplifier 151 n to generate a monitoring voltage Efnproportionate to a load current Ifn at the electrical load 103 n. Anon-inverting input terminal of the differential amplifier 151 n isconnected to a point of connection between the switching element 181 nand the current detection resistor 141 n through first and second seriesresistors 142 n and 152 n. A first negative voltage suppressing diode144 n is connected between a point of connection between the first andsecond series resistors 142 n and 152 n and the internal ground circuitGND2 of the power supply control unit 100B. An inverting input terminalof the differential amplifier 151 n is connected to a point ofconnection between the current detection resistor 141 n and theelectrical load 103 n through third and fourth series resistors 143 nand 153 n. A second negative voltage suppressing diode 145 n isconnected between a point of connection between the third and fourthseries resistors 143 n and 153 n and the internal ground circuit GND2 ofthe power supply control unit 100B. Thus, an excessively high negativevoltage applied to the differential amplifier 151 n when there is abreakage at the external individual negative lines 104 n for thecommutation diodes 146 n is suppressed by the first and second negativevoltage suppressing diodes 144 n and 145 n. This configuration ischaracterized in that damage to the differential amplifier 151 n by asurge voltage generated by the electrical load 103 n can be preventedwhen there is a breakage at the external individual negative lines 104n. The configuration is also characterized in that a surge currentsuperimposed on the internal ground circuit GND2 of the power supplycontrol unit 100B when a breakage occurs at the external individualnegative lines 104 n can be suppressed to a very small value by thefirst and third series resistors 142 n and 143 n.

In Embodiment 2, the power supply state detection circuits PDETBn haveload voltage monitoring circuits 300 a to 300 c (hereinafter representedby 300 n), respectively. A load voltage monitoring circuit 300 nincludes an analog input circuit which inputs a voltage proportionate tothe load voltage Vfn applied to one resistor 302 n of a couple ofvoltage dividing resistors 301 n and 302 n connected between a point ofconnection between the current detection resistor 141 n and theelectrical load 103 n and the internal ground circuit GND2 of the powersupply control unit 100B to the microprocessor 120B. A clip diode 305 nconnected to the internal ground circuit GND2 at an anode terminalthereof is connected in parallel with the resistor 302 n of the coupleof voltage dividing resistors 301 n and 302 n. The clip diode 305 nsuppresses an excessively high negative voltage applied to the loadvoltage monitoring circuit 300 n when there is a breakage at theexternal individual negative lines 104 n associated with the commutationdiodes 146 n. This configuration is characterized in that damage to theload voltage monitoring circuit 300 n attributable to a surge voltagegenerated by the electrical load 103 n can be prevented when there is abreakage at the external individual negative lines 104 n. Theconfiguration is also characterized in that a surge current superimposedon the internal ground circuit GND2 of the power supply control unit100B when a breakage abnormality occurs at the external individualnegative lines 104 n can be suppressed to a very small value by theother resistor 301 n of the couple of voltage dividing resistors 301 nand 302 n.

In Embodiment 2, the power supply control circuit PCNTB includesnegative feedback control circuits 190 a to 190 c (hereinafterrepresented by 190 n). The non-volatile program memory 121B includes acontrol program including target current command means 850 whichconstitutes the energization command means. A power supply voltagemeasurement signal Vd which is an analog signal supplied by a powersupply voltage measurement circuit 115 and a load voltage measurementsignal Vfn which is an analog signal supplied by a load voltagemonitoring circuit 300 n are input to the microprocessor 120B. Thetarget current command means 850 is means for generating a settingcommand output ITn having a variable duty an proportionate to anenergization target current Isn for an electrical load 103 n. Thenegative feedback control circuit 190 n controls the turning on/off ofthe switching element 181 n by generating the energization commandoutput DRn having a variable duty γn in accordance with an integratedvalue of a deviation between a set voltage Esn proportionate to a targetcurrent Isn obtained by smoothing the setting command output ITn and amonitoring voltage Efn proportionate to the load current Ifn detected bythe differential amplifier 150 n for current detection. The power supplyvoltage measuring circuit 115 includes voltage dividing resistors 111and 112 for dividing the driving power supply voltage Vb supplied by theDC driving power supply 101 and inputting the resultant voltage to themicroprocessor 120B. The load voltage monitoring circuit 300 n is ananalog circuit which supplies the microprocessor 120B with a loadvoltage measurement input Vfn proportionate to the load voltage Vfnapplied to one resistor 302 n of the couple of voltage dividingresistors 301 n and 302 n connected between a point of connectionbetween the current detection resistor 141 n and the electrical load 103n and the internal ground circuit GND2 of the power supply control unit100B. This configuration is characterized in that the control burden ofthe microprocessor 120B can be distributed between the plurality ofelectrical loads 103 n to perform highly accurate current control. Theconfiguration is also characterized in that various abnormalities can bedetermined by providing the microprocessor 120B with a feedback ofmonitoring signals in analog values representing load voltages Vfn.

In Embodiment 2, the power supply control circuit PCNTB includes leakageresistors 149 n having a high resistance connected in parallel with theswitching elements 181 n and load voltage dividing circuits 1410 nprovided on the output side of the switching elements 181 n. Thenon-volatile program memory 121B includes a program including first andsecond comparison/determination means 820 b and 820 a for comparing aload voltage Vfn obtained by a load voltage monitoring circuit 300 nwith each of first and second threshold voltages V1 and V2. A leakageresistor 149 n supplies such a very small load current that theelectrical load 103 n will not be activated when the switching element181 n is off. The load voltage dividing circuit 1410 n includes a bypassresistor 147 n which is connected between either a point connecting theswitching element 181 n and the current detection resistor 141 n or apoint connecting the current detection resistor 141 n and the electricalload 103 n and either the anode terminal A of the commutation diode 146n or the internal ground circuit GND2 of the power supply control unit100B. The first threshold voltage V1 is proportionate to a voltageapplied to the bypass resistor 147 n through the leakage resistor 149 nat the time of occurrence of a breakage abnormality including a breakageat any of the electrical load 103 n, the positive side wiring 103P ofthe electrical load 103 n, and the negative side wiring 103N of theelectrical load 103 n. The second threshold voltage V2 is proportionateto a voltage applied to the bypass resistor 147 n at the time ofoccurrence of either shorting abnormality at the switching element 181 nor power line shorting that the positive side wiring 103P of theelectrical load 103 n is contacted to the power supply line. When thebreakage abnormality occurs, the output logic of the firstcomparison/determination means 820 b is inverted to provide a notice ofthe breakage abnormality. When there is either shorting abnormality atthe switching element 181 n or power line shorting abnormality at thepositive side wiring 103P of the electrical load 103 n, the output logicof the second comparison/determination means 820 a is inverted toprovide a notice of the abnormality. This configuration is characterizedin that identification or determination can be made before energizationis started with a simple detection circuit on whether there is abreakage abnormality at an electrical load 103 n or a breakageabnormality at the positive side wiring 103P or negative side wiring103N of the same or whether there is a power line shorting abnormalityat the positive side wiring 103P or a shorting abnormality at theswitching element 181 n.

In Embodiment 2, the non-volatile program memory 121B includes a controlprogram including load resistance estimation means 808 and at leasteither under-resistance determination means 840 or over-resistancedetermination means 830. The load resistance estimation means 808performs a calculation to estimate a current resistance value Rn of anelectrical load 103 n, which is equivalent to Vfn/Isn, based on a loadvoltage Vfn measured by the load voltage monitoring circuit 300 n and atarget command current Isn instructed by a target current command means850. The under-resistance determination means 840 generates anabnormality determination output when the load resistance Rn estimatedby the load resistance estimation means 808 is smaller than a minimumload resistance Rmin in a low temperature environment, thereby providinga notice of the occurrence of any of a shorting abnormality at theelectrical load 103 n, a grounding abnormality that is contact betweenthe positive side wiring 103P and the vehicle body, and a shortingabnormality at the switching element 181 n in the duration of theenergization command for the switching element 181 n. Theover-resistance determination means 830 generates an abnormalitydetermination output when the load resistance Rn estimated by the loadresistance estimation means 808 is greater than a maximum loadresistance Rmax in a high temperature environment, thereby providing anotice of the occurrence of any of a breakage abnormality at theelectrical load 103 n, a breakage abnormality at the positive sidewiring 103P, a breakage abnormality at the negative side wiring 103N, apower line shorting abnormality at the positive side wiring 103P, and abreakage abnormality at the switching element 181 n in the duration ofthe energization command for the switching element 181 n. Thisconfiguration is characterized in that it is possible to detect abnormalstates using inexpensive means without relying on hardware, the abnormalstates including breakage abnormalities at the electrical loads 103 n,power line shorting abnormalities at the positive side wirings 103P,shorting abnormalities at the electrical loads 103 n, groundingabnormalities at the positive side wirings 103P, breakage abnormalitiesat the switching elements 181 n, and shorting abnormalities at theswitching elements 181 n.

In Embodiment 2, the over-resistance determination means 830 furtherincludes a confirmative determination means 832. When theover-resistance determination means 830 determines that there is a stateof over-resistance, the confirmative determination means 832 stores thefact that neither the shorting abnormality at the switching element 181n nor power line shorting abnormality at the positive side wiring 103Phas occurred as abnormality history information if the load voltage Vfnhas dropped after the setting command output ITn to the negativefeedback control circuit 190 n was stopped. This configuration ischaracterized in that the efficiency of maintenance and inspectionoperations can be improved by identifying and storing the cause of astate of over-resistance as a power line shorting abnormality at apositive side wiring 103P, a breakage abnormality at an electrical load103 n or a shorting abnormality at a switching element 181 n.

In Embodiment 2, the abnormality processing means 811, 821, 831, and 841provide an abnormality notice by stopping the energization command to anelectrical load not only when a breakage abnormality is detected at thenegative line but also when either of a shorting abnormality at anelectrical load 103 n or a grounding abnormality at the positive sidewiring 103P of an electrical load 103 n is detected. The abnormalityhistory storing means 813, 823, 843, 833 a, and 833 b write and storeinformation on a shorting abnormality at an electrical load 103 n and agrounding abnormality at a positive side wiring 103P in the data memory123 in addition to the history of occurrence of breakage abnormalities.This configuration is characterized in that comprehensive historyinformation can be stored in accordance with the contents ofabnormalities to facilitate maintenance and inspections because anenergization command to an electrical load 103 n is stopped and anabnormality notice is provided not only when there is a breakageabnormality but also when there is a shorting abnormality at theelectrical load 103 n or a grounding abnormality at the positive sidewiring 103P thereof.

Embodiment 3 (31) Configuration of Embodiment 3

FIG. 9 is a general circuit diagram of Embodiment 3 of a power supplycontrol device for on-vehicle electrical loads according to theinvention. The configuration of Embodiment 3 will be described withreference to FIG. 9 with the focus of the description put on differencesfrom Embodiment 1 shown in FIG. 1 and Embodiment 2 shown in FIG. 5, andparts identical or equivalent to those in FIG. 1 are indicated by likereference numerals and signs.

In Embodiment 3, as shown in FIG. 9, a power supply control unit 100C isused instead of the power supply unit 100A used in Embodiment 1. Thepower supply control unit 100C controls supply of power from a DCdriving power supply 101 to a group of on-vehicle electrical loads. Thegroup of on-vehicle electrical loads includes a load circuit 103. Theload circuit 103 includes a plurality of electrical loads which are, forexample, six electrical loads 103 a to 103 f in FIG. 9. The electricalloads 103 a to 103 f are inductive on-vehicle electrical loads. Anegative terminal of each of the electrical loads 103 a to 103 f isconnected to the vehicle body at a load ground GND3. The control unit100C controls supply of power from the DC driving power supply 101 tothe electrical loads 103 a to 103 f.

The power supply control unit 100C is contained in a sealed housing 100a. The power supply control unit 100C includes a power supply inputterminals ES1, ES2, and ES3, a unit ground terminal GND, load outputterminals LD1 to LD6, and two common terminals COM1 and COM2. Each ofthe terminals is disposed in the housing 100 a and electricallyinsulated from the housing 100 a. The power supply input terminals ES1,ES2, and ES3 and the unit ground terminal GND are configured similarlyto those in Embodiment 1. The load output terminals LD1 to LD6 areprovided in association with the electrical loads 103 a to 103 f. Theunit ground terminal GND is connected to a vehicle body at a unit groundGND1 along with an internal ground circuit GND2 just as in Embodiment 1.

The common terminals COM1 And COM2 of the power supply control unit 100Care connected to the vehicle body at a separated ground GND4 in thevicinity of the common terminals COM1 and COM2 through external commonnegative lines 104 x and 104 y, respectively. The terminals areconnected to a load ground GND3 through the vehicle body and connectedto negative side wirings 103N of the electrical loads 103 a to 103 f.The distance between the separated ground GND4 and the load ground GND3is smaller than the distance between the separated ground GND4 and theunit ground GND1. As a result, resistance between the separated groundGND4 and the load ground GND3 is smaller than resistance between theseparated ground GND4 and the unit ground GND1, and fluctuations of anelectric potential at the vehicle body attributable to commutation atthe electrical loads 103 a to 103 f can therefore be kept small.

The power supply control unit 100C incorporates load power supplycircuits SPLa to SPLf associated with the electrical loads 103 a to 103f, load commutation circuits SWLa to SWLf, and a power supply controlcircuit PCNTC. The power supply control circuit PCNTC is primarilyconstituted by a microprocessor 120C. The power supply control circuitPCNTC includes a control power supply circuit 110, switching circuits180 a to 180 f, commutation circuits 2400 a to 2400 f, an individualabnormality detection circuit IADETC, and a negative line breakageabnormality detection circuit 160C. The individual abnormality detectioncircuit IADETC detects individual abnormalities at the electrical loads103 a to 103 f, and the negative line breakage abnormality detectioncircuit 160C detects abnormalities at the external common negative lines104 x and 104 y.

The individual abnormality detection circuit IADETC is constituted bypower supply state detection circuits PDETCa to PDETCf provided inassociation with the electrical loads 103 a to 103 f, respectively, andthe microprocessor 120C. The power supply state detection circuit PDETCaassociated with the electrical load 103 a includes a current detectioncircuit 240 a, a current detecting differential amplifier circuit 150 a,a negative feedback control circuit 190 a, a load voltage monitoringcircuit 300 a, and an over-current detection circuit 350 a. Similarly,the power supply state detection circuit PDETCf associated with theelectrical load 103 f includes a current detection circuits 240 f, acurrent detecting differential amplifier circuit 150 f, a negativefeedback control circuit 190 f, a load voltage monitoring circuit 300 f,and an over-current detection circuit 350 f.

The current detecting differential amplifier circuits 150 a to 150 f areconfigured similarly to those in Embodiment 1. The microprocessor 120Cis used instead of the microprocessor 120A in Embodiment 1. Theswitching circuits 180 a to 180 f, the negative feedback controlcircuits 190 a to 190 f, and the load voltage monitoring circuits 300 ato 300 f are configured similarly to those in Embodiment 2. Thecommutation circuits 2400 a to 2400 f are provided by modifying theconfiguration of the commutation circuits 1400 a to 1400 c of Embodiment1, and the current detection circuits 240 a to 240 f are provided bymodifying the configuration of the current detection circuits 140 a to140 c of Embodiment 1. The over-current detection circuits 350 a to 350f are elements newly provided in the power supply control unit 100C ofEmbodiment 3. The negative line breakage abnormality detection circuit160C is used instead of the negative line breakage abnormality detectioncircuit 160A in Embodiment 1.

The load power supply circuits SPLa to SPLf are formed between the powersupply input terminal ES1 and the load output terminals LD1 to LD6 inthe same way as in Embodiment 1. The load commutation circuits SWLa toSWLc of the power supply control unit 100C are formed between the commonterminal COM1 and the load power supply circuits SPLa to SPLc,respectively. Similarly, the load commutation circuits SWLd to SWLf areformed between the common terminal COM2 and the load power supplycircuits SPLd to and SPLf, respectively. Specifically, the loadcommutation circuits SWLa to SWLc are connected to the common terminalCOM1 at one end thereof and connected to the load power supply circuitsSPLa to SPLc between the switching circuits 180 a to 180 c and thecurrent detection circuit 240 a to 240 c, respectively, at another endthereof. Similarly, the load commutation circuits SWLd to SWLf areconnected to t common terminal COM2 at one end thereof and connected tothe load power supply circuits SPLd to SPLf between the switchingcircuits 180 d to 180 f and the current detection circuit 240 d to 240f, respectively, at another end thereof. The commutation circuits 2400 ato 2400 f are disposed at the load commutation circuits SWLa to SWLf,respectively.

The microprocessor 120C, which is a major constituent part of the powersupply control circuit PCNTC, is bus-connected to a non-volatile programmemory 121C constituted by, for example, a non-volatile flash memorywhich can be electrically erased at once to allow writing and which canbe read, a RAM memory 122 for arithmetic processes, a data memory 123constituted by a non-volatile EEPROM which can be electrically writtenand read byte by byte, and a multi-channel A-D converter 124. Themicroprocessor is configured for mutual cooperation with those elements.

The switching circuits 180 a to 180 f are supplied with power from theDC driving power supply 101 through a load power supply relay contact102 b and the power supply input terminal ES1. The circuits 180 a to 180f supply power to the electrical loads 103 a to 103 f through currentdetection resistors 141 a to 141 f of the current detection circuits 240a to 240 f and the load output terminals LD1 to LD6, respectively. Theswitching circuits 180 a to 180 f are turned on/off under the control ofenergization command outputs DR1 to DR6 generated by the negativefeedback control circuits 190 a to 190 f to supply the electrical loads103 a to 103 f with load voltages proportionate to energization dutieswhich are ratios of on-times to on/off periods. Details of the currentdetection circuit 240 a will be described later with reference to FIG.10.

Commutation diodes 2400 a to 2400 f are provided in the load commutationcircuits SWLa to SWLf, respectively. Commutation diodes 146 a to 146 fof the commutation circuits 2400 a to 2400 f are connected in parallelwith series circuits formed by the current detection resistors 141 a to141 f and the electrical loads 103 a to 103 f, respectively. Anodeterminals A of the commutation diodes 146 a to 146 c associated with theelectrical loads 103 a to 103 c are commonly connected to the commonterminal COM1. Similarly, anode terminals A of the commutation diodes146 d to 146 f associated with the electrical loads 103 d to 103 f arecommonly connected to the common terminal COM2. Details of thecommutation circuit 2400 a will be described later with reference toFIG. 10.

The current detecting differential amplifier circuits 150 a to 150 f areconfigured similarly to the current detecting differential amplifiercircuit 150 a in Embodiment 1. The current detecting differentialamplifier circuits 150 a to 150 f perform differential amplification ofvoltages across the current detection resistors 141 a to 141 f,respectively, to supply monitoring voltages Ef1 to Ef6 proportionate toload currents If1 to If6 flowing through the electrical loads 103 a to103 f to inputs of the negative feedback control circuits 190 a to 190 fon one side thereof. The over-current detection circuits 350 a to 350 fare inputted to the micro processor 120C with generation of an alarmsignals OC1 to OC6 when the output voltage of the corresponding currentdetecting differential amplifier circuits 150 a to 150 f exceeds thepredetermined value.

Based on a program serving as a target current command means stored inthe non-volatile program memory 121C, the microprocessor 120C generatesoutputs IT1 to IT6 commanding setting of energization duties α1 to α6proportionate to target current values Is1 to Is6, respectively, andsupplies the setting command outputs IT1 to IT6 to other inputs of thenegative feedback control circuits 190 a to 190 f. The negative feedbackcontrol circuits 190 a to 190 f generate energization command outputsDR1 to DR6 having variable duties in accordance with integrated valuesof deviations between set voltages Es1 to Es6 which are proportionate tothe target current values Is1 to Is6 obtained by smoothing the settingcommand outputs IT1 to IT6 and the monitoring voltages Ef1 to Ef6 whichare proportionate to the load current values If1 to If6 detected by thecurrent detecting differential amplifier circuits 150 a to 150 f,respectively. The circuits thus control the turning on/off the switchingelement 181 a to 181 f of the switching circuits 180 a to 180 f with theenergization command outputs DR1 to DR6. The negative line breakageabnormality detection circuit 160C detects breakages at the externalcommon negative lines 104 x and 104 y and breakages at the negativelines attributable to contact failures at the common terminals COM1 andCOM2 and supplies the alarm signal MNT to the microprocessor 120C.Details of the negative line breakage abnormality detection circuit 160Cwill be described later with reference to FIG. 10.

The load voltage monitoring circuits 300 a to 300 f monitor voltages atthe load output terminals LD1 to LD6 to which positive side wirings 103Pof the electrical loads 103 a to 103 f are connected respectively andsupplies load voltage measurement inputs Vf1, which are analog signalsproportionate to load voltages Vf1 to Vf6, to the microprocessor 120C.

The switching circuits 180 b to 180 f, the current detection circuits240 b to 240 f, the current detecting differential amplifier circuits150 b to 150 f, the over-current detection circuits 350 b to 350 f, theload voltage monitoring circuits 300 b to 300 f, and the negativefeedback control circuits 190 b to 190 f associated with the electricalloads 103 b to 103 f are configured similarly to the switching circuit180 a, the current detection circuit 240 a, the current detectingdifferential amplifier circuit 150 a, the over-current detection circuit350 a, the load voltage monitoring circuit 300 a, and the negativefeedback control circuit 190 a associated with the electrical load 103a, respectively. The microprocessor 120C generates the setting commandoutputs IT1 to IT6 and operates on the load voltage measurement inputsVf1 to Vf6 and the power supply voltage measurement input Vd as analoginputs and the alarm signals OC1 to OC6 as logical signal inputs.

FIG. 10 is a detailed circuit diagram of a major part of Embodiment 3shown in FIG. 9. FIG. 10 shows details of the current detection circuit240 a, the commutation circuit 2400 a, the negative feedback controlcircuit 190 a, the current detecting differential amplifier circuit 150a, the over-current detection circuit 350 a, and the negative linebreakage abnormality detection circuit 160C which are associated withthe electrical load 103 a. The description will be made with referenceto FIG. 10 and will be focused on differences from what is shown inFIGS. 2 and 6. The current detection circuits 240 b to 240 f, thecommutation circuits 2400 b to 2400 f, the negative feedback controlcircuits 190 b to 190 f, the current detecting differential amplifiercircuits 150 b to 150 f, and the over-current detection circuits 350 bto 350 f associated with the other electrical loads 103 b to 103 f areconfigured similarly to the current detection circuit 240 a, thecommutation circuit 2400 a, the negative feedback control circuit 190 a,the current detecting differential amplifier circuit 150 a, and theover-current detection circuit 350 a shown in FIG. 10, respectively.

Referring to FIG. 10, the switching circuit 180 a, the current detectingdifferential amplifier circuit 150 a, the negative feedback controlcircuit 190 a, and the load voltage monitoring circuit 300 a are similarin configuration to those in FIG. 6. In the current detection circuit240 a, a bypass resistor 147 a connected in parallel with thecommutation diode 146 a is incorporated in the current detection circuit240 a, and the bypass resistor 147 a form a load voltage dividingcircuit 1420 a in combination with a leakage resistor 149 a and a blockdiode 148 a. One end of the bypass resistor 147 a is connected to theload output terminal LD1, and another end of the resistor is connectedto the internal ground circuit GND2 of the power supply control unit100C. A cathode terminal K of the block diode 148 a is connected to theinternal ground circuit GND2, and an anode terminal A of the diode isconnected to the bypass resistor 147 a. One terminal of the bypassresistor 147 a may be connected either side of the current detectionresistor 141 a, and another terminal of the resistor 147 a may beconnected to the anode terminal of the commutation diode 146 a. The loadvoltage dividing circuit 1420 a has a function similar to that of theload voltage dividing circuit 1410 a in embodiments 1 and 2.

The over-current detection circuit 350 a includes a comparison/detectioncircuit 351 a, an output resistor 358 a, a smoothing capacitor 359 a,and voltage dividing resistors 354 a and 355 a. The output resistor 358a supplies the alarm signal OC1 to the microprocessor 120C. The voltagedividing resistors 354 a and 355 a divide an output voltage E0 of adifferential amplifier 151 a of the current detecting differentialamplifier circuit 150 a and supplies the resultant voltage to aninverting input terminal of the comparison/determination circuit 351 a.The control power supply voltage Vcc is applied to an non-invertinginput terminal of the comparison/determination circuit 351 a.

In Embodiment 3, the output voltage E0 of the differential amplifier 151a of the current detecting differential amplifier circuit 150 a is avoltage upstream of the monitoring voltage Ef1 input to the negativefeedback control circuit 190 a. The monitoring voltage Ef1 is clamped bya voltage clamping diode 356 a such that will not equal or exceed thelevel of the control power supply voltage Vcc. An anode terminal A ofthe voltage clamping diode 356 a is connected to the output resistor 158a of the current detecting differential amplifier circuit 150 a, and acathode terminal K of the diode is connected to the control power supplyvoltage Vcc. Since the differential amplifier 151 a in Embodiment 3operates on the driving power supply voltage Vb, the output voltage E0normally varies within the range from 0 to Vcc (=5 volts) depending onthe magnitude of the load current flowing through the electrical load103 a. However, the voltage E0 increases to equal the voltage Vb (=10 to16V) when an abnormality such as a shorting fault of the switchingelement 181 a of the switching circuit 180 a occurs.

The negative line breakage abnormality detection circuit 160C has adetermination element 161 constituted by a PNP transistor to which thecontrol power supply voltage Vcc is supplied. A connector terminal C ofthe determination element 161 is connected to the internal groundcircuit GND2 through a collector resistor 162 and is also connected toan alarm signal terminal of the microprocessor 120C through an outputresistor 163 a. The integrating capacitor 163 b is charged from theoutput resistor 163 a to form a smoothing circuit.

A stabilizing resistor 164 for an off-state of the determination element161 is connected between an emitter terminal E and a base terminal B ofthe determination element 161. The base terminal B of the determinationelement 161 is connected to the common terminals COM1 and COM2 through abase resistor 165, a current limiting resistor 166, a constant voltagediode 167, and combined diodes 169 x and 169 y. An anode terminal A of aclip diode 168 is connected to the internal ground circuit GND2, and acathode terminal of the diode is connected to a point of connectionbetween the base resistor 165 and the current limiting resistor 166.

When any of the switching circuits 180 a to 180 c interrupts the loadcurrent while there is a breakage at the external common negative line104 x connected to the common terminal COM1, the determination element161 is caused to be conducting by a surge current which flows from thebase resistor 165 to the load output terminals LD1 to LD3 via thecurrent limiting resistor 166, the constant voltage diode 167, thecombined diode 169 x, the commutation diodes 146 a to 146 c, and thecurrent detection resistors 141 a to 141 c. The determination elementthus changes the logical level of the alarm signal MNT to “H” to inputthe occurrence of the negative line breakage abnormality to themicroprocessor 120C.

Similarly, when any of the switching circuits 180 d to 180 f interruptsthe load current while there is a breakage at the external commonnegative line 104 y connected to the common terminal COM2, thedetermination element 161 is caused to be conducting by a surge currentwhich flows from the base resistor 165 to the load output terminals LD4to LD6 via the current limiting resistor 166, the constant voltage diode167, the combined diode 169 y, the commutation diodes 146 d to 146 f,and the current detection resistors 141 d to 141 f. The determinationelement thus changes the logical level of the alarm signal MNT to “H” toinput the occurrence of the negative line breakage abnormality to themicroprocessor 120C.

The determination element 161 detects negative electric potentialsgenerated at the anode terminals A of the commutation diodes 146 a to146 f when the load currents to the electrical loads 103 a to 103 f areinterrupted to generate the alarm signal MNT. When the common terminalsCOM1 and COM2 are properly connected to the vehicle body through theexternal common negative lines 104 x and 104 y, no electric potential isgenerated at the anode terminals A of the commutation diodes 146 a to146 f, and the alarm signal MNT generated by the determination element161 is at the logical level “L” which indicate a normal state.

(32) Effects and Operations of Embodiment 3

Effects and operations of Embodiment 3 of the invention shown in FIGS. 9and 10 will now be described. Referring to FIG. 9, when a power supplyswitch which is not shown is turned on, the power supply switching relaycontact 102 a is turned on to apply the driving power supply voltage Vbto the control power supply circuit 110, and the control power supplycircuit 110 generates the control power supply voltage Vcc and suppliesit to the microprocessor 120C. When the microprocessor 120C startsoperating, the load power supply relay contact 102 b is turned on by anenergization circuit which is not shown. Based on an operation controlprogram stored in the non-volatile program memory 121C, themicroprocessor 120C determines which of the plurality of electricalloads 103 a to 103 f is to be supplied with a load current anddetermines the amount of the load current. The microprocessor thereaftergenerates the setting command outputs IT1 to IT6 which are pulse outputsof the energization duties α1 to α6 proportionate to the target loadcurrent values Is1 to Is6 based on a control program to serve as atarget current command means stored in the non-volatile program memory121C.

The negative feedback control circuit 190 a controls the turning on/offof the switching element 181 a of the switching circuit 180 a bygenerating the energization command output DR1 having a variable duty γ1in accordance with an integrated value of a deviation between the setvoltage Es1 which is proportionate to the target load current value Is1for the electrical load 103 a obtained by smoothing the setting commandoutput IT1 and the monitoring voltage Ef1 which is proportionate to theload current If1 detected by the current detecting differentialamplifier circuit 150 a. The other negative feedback control circuits190 b to 190 f operate in the same manner.

When the switching element 181 a is on, the load current If1 flows fromthe positive terminal of the DC driving power supply 101 and circulatesthrough a path formed by the load power supply relay contact 102 b, thepower supply input terminal ES1, the switching element 181 a, thecurrent detection resistor 141 a, load output terminal LD1, the positiveside wiring 103P, the electrical load 103 a, the negative side wiring103N, the load ground GND3, the vehicle body, and a power supply groundGND0 back to the negative terminal of the DC driving power supply 101.No load current flows to the internal ground circuit GND2 of the powersupply control unit 100C at all. When the switching element 181 a isturned off, the load current If1 flows from the negative terminal offthe electrical load 103 a and circulates through a path formed by thenegative side wiring 103N, the load ground GND3, the vehicle body, theseparated ground GND4, the external common negative line 104 x, thecommon terminal COM1, the commutation diode 146 a, the current detectionresistor 141 a, the load output terminal LD1, and the positive sidewiring 103P back to the positive terminal of the electrical load 103 a.In this case again, no load current flows to the internal ground circuitGND2 of the power supply control unit 100C at all. The load currents If2to If6 of the electrical loads 103 b to 103 f flow similarly. The abovedescription holds true when the external common negative lines 104 x and104 y are extended to the position of the load ground GND3 instead ofconnecting them to the vehicle body at the separated ground GND4.

Let us now assume that the external common negative lines 104 x to 104 yare not provided and that the anode terminal A of the commutation diode146 a is connected to the internal ground circuit GND2 of the powersupply control unit 100C. In this case, when the switching element 181 ais turned off, the load current If1 flows from the negative terminal ofthe electrical load 103 a and circulates through a path formed by thenegative side wiring 103N, the load ground GND3, the unit ground GND1,the unit ground terminal GND, the internal ground circuit GND2, thecommutation diode 146 a, the current detection resistor 141 a, the loadoutput terminal LD1, and the positive side wiring 103P back to thepositive terminal of the electrical load 103 a. A problem arises in thata commutation surge current flows into the internal ground circuit GND2to cause fluctuations of the electric potential at the internal groundcircuit GND2.

In Embodiment 3, the anode terminals A of the commutation diodes 146 ato 146 f are connected to the vehicle body outside the power supplycontrol unit 100C, which makes it possible to prevent the load currentsIf1 to If6 from flowing into the internal ground circuit GND2 of thepower supply control unit 100C. On the contrary, when there is a contactfailure at the common terminals COM1 and COM2 or a breakage abnormalityat the external common negative lines 104 x and 104 y, the commutatingfunction of the commutation diodes 146 a to 146 f is deteriorated, whichresults in another problem in that an induced surge voltage is generatedby inductive components of the electrical loads 103 a to 103 f when theswitching elements 181 a to 181 f are turned off. The surge voltage issuppressed to, for example, about 50 volts by voltage clamping diodes184 a (see FIG. 6) for suppressing an off-voltage provided at theswitching elements 181 a to 181 f. However, the suppressed surge voltagewill be applied to all circuits in the power supply control unit 100Cwhich are connected between the internal ground circuit GND2 and theload output terminals LD1 to LD6.

Referring to FIG. 6, the block diode 148 a of the current detectioncircuit 240 a blocks a countercurrent attributable to the suppressedsurge voltage. First and second negative voltage suppressing diodes 144a and 145 a of the current detection circuit 240 a suppress inputelectric potentials of the differential amplifier 151 a of the currentdetecting differential amplifier 150 a to negative electric potentialsof, for example, about 1 volt that is the forward voltage of the firstand second negative voltage suppressing diodes 144 a and 145 a. Thefirst and third series resistors 142 a and 143 a of the currentdetection circuit 240 a suppress a surge current which circulates fromthe unit ground GND1 to the load output terminal LD1 via the internalground circuit GND2 and the first or second negative voltage suppressingdiode 144 a or 145 a, thereby suppressing fluctuations of the electricpotential at the internal ground circuit GND2. Effects and operations ofthe each part of the circuits corresponding to the electrical loads 103b to 103 f (not shown) are similar to those described above with respectto the electrical load 103 a.

The base resistor 165, the current limiting resistor 166, the constantvoltage diode 167, and the clip diode 168 of the negative line breakageabnormality detection circuit 160C have effects similar to those shownin FIG. 3. When there is a breakage at the external common negativelines 104 x and 104 y connected to the common terminals COM1 and COM2,the determination element 161 is turned on by the commutation surgecurrent, the logical level of the alarm signal MNT is changed to “H” toinput the occurrence of the breakage abnormality at the negative linesto the microprocessor 120C.

While the external common negative line 104 is used in FIG. 3, theexternal common negative lines 104 x and 104 y are used in Embodiment 3as shown in FIG. 9. The common terminal COM is also divided into the twocommon terminals COM1 and COM2. Thus, no concentration of currentscommutated from the electrical loads 103 a to 103 f occurs at the commonterminals COM1 and COM2, and it is therefore possible to prevent anover-current from flowing to the common terminals COM1 and COM2.Although it is desirable to extend the external common negative lines104 x and 104 y to the position of the load ground GND3, they areconnected to the vehicle body in the position of the separated groundGND4 provided in the vicinity of the common terminals COM1 and COM2 inorder to keep the number of wirings small.

When the over-current detection circuits 350 a to 350 f generate thealarm signals OC1 to OC6, the microprocessor 120C stops the settingcommand outputs IT1 to IT6 using a control program which is not shownand stores the information of the occurrence of an over-currentabnormality in the data memory 123 as abnormality history information.The operation of Embodiment 3 is otherwise similar to that shown in theflow chart in FIG. 8.

(33) Summaries and Characteristics of Embodiment 3

Embodiment 3 can be summarized and characterized as follows.

As apparent from the above description, the power supply control devicefor on-vehicle electrical loads according to Embodiment 3 of theinvention is a power supply control device comprising a power supplycontrol unit 100C. The power supply control unit 100C includes aplurality of load power supply circuits SPLa to SPLf (hereinafterrepresented by SPLn) for supplying power from a DC driving power supply101 to a plurality of electrical loads 103 a to 103 f (hereinafterrepresented by 103 n), respectively, through switching elements 181 a to181 f (hereinafter represented by 181 n), a plurality of loadcommutation circuits SWLa to SWLf (hereinafter represented by SWLn) forcommutating load currents to the electrical loads 103 n, and a powersupply control circuit PCNTC for supplying energization command outputsDRn to the switching elements (181 n). The load power supply circuitsSPLn, the load commutation circuits SWLn, and the power supply controlcircuit PCNTC are contained in a housing 100 a of the power supplycontrol unit 100C. The power supply control device is characterized asfollows. Commutation diodes 146 a to 146 f (hereinafter represented by146 n) are provided to the load commutation circuits SWLn, respectively,and the commutation diodes 146 n are connected in parallel with therespective electrical loads 103 n to cause currents which have beenflowing through the electrical loads 103 n to flow back when theswitching elements 181 n of the load power supply circuits SPLn areturned off. The commutation diodes 146 n are connected to a vehicle bodyoutside the housing 100 a separately from an internal ground circuitGND2 of the power supply control unit 100C by external common negativelines 104 x and 104 y constituting an external negative line. The powersupply control circuit PCNTC includes an individual abnormalitydetection circuit IADETC, a negative line breakage abnormality detectioncircuit 160C, abnormality processing means 811, 821, 831, and 841, andabnormality history storing means 813, 823, 843, 833 a, and 833 b. Thepower supply control circuit PCNTC is configured by using amicroprocessor 120C. The microprocessor 120C is configured to operate inconjunction with a non-volatile program memory 121C in which at least acontrol program serving as an energization command means for theswitching elements 181 n is stored, a data memory 123, a RAM memory 122for arithmetic processes, and a multi-channel A-D converter 124. Theindividual abnormality detection circuit IADETC includes a plurality ofpower supply state detection circuits PDETCa to PDETCf (hereinafterrepresented by PDETCn) for detecting amounts of power, specifically,load currents Ifn supplied to the electrical loads 103 n and means fordetermining an individual abnormal state when the amount of powersupplied to a certain electrical load among the electrical loads 103 ndeviates from a target amount of supplied power. The individual abnormalstate is either breakage or shorting of at least one of the electricalload, the positive side wiring 103P of the electrical load, the negativeside wiring 103N of the electrical load, and the switching elementassociated with the electrical load. The negative line breakageabnormality detection circuit 160C is a circuit for determining abreakage abnormality at the external common negative lines 104 x and 104y by detecting that an electric potential on an anode side of eachcommutation diode 146 n is different from an electric potential at theinternal ground circuit GND2 of the power supply control unit 100C. Theabnormality processing means 811, 821, 831, and 841 are means forstopping the energization command output to the switching elements whenat least either an individual abnormality or a breakage abnormality atthe external individual negative lines 104 n is detected and forproviding a notice of the abnormality. The abnormality history storingmeans 813, 823, 843, 833 a, and 833 b are means for storing and savingthe history of occurrence of individual abnormalities and breakageabnormalities at the external common negative lines 104 x and 104 y inthe data memory 123 with identification of the abnormalities.

In the power supply control device for on-vehicle electrical loads inEmbodiment 3, the commutation diodes 146 n connected in parallel withthe plurality of electrical loads 103 n, respectively, supplied withpower from the DC driving power supply 101 through the respectiveswitching elements 181 n are connected to the vehicle body outside thehousing 100 a of the power supply control unit 100C separately from theinternal ground circuit GND2 of the power supply control unit 100C bythe external common negative lines 104 x and 104 y. Therefore, neitherload current nor commutation current flows to the internal groundcircuit GND2 of the power supply control unit 100C, which isadvantageous in that the electric potential at the internal groundcircuit GND2 can be stabilized to allow the power supply control circuitPCNTC of the power supply control unit 100C to be operated withstability. Breakage abnormalities and shorting abnormalities at theelectrical loads 103 n, the positive side wirings 103P thereof, thenegative side wirings 103N thereof, and the switching elements 181 n aredetected by the individual abnormality detection circuit IADETC, andbreakages at the external common negative lines 104 x and 104 yassociated with the commutation diodes 146 n are detected by thenegative line breakage abnormality detection circuit 160C. Measures aretaken against those abnormalities, and the abnormalities are identifiedand stored by the abnormality history storing means 813, 823, 843, 833a, and 833 b. Therefore, the efficiency of maintenance and inspectioncan be advantageously improved by reading history information at thetime of maintenance and inspection.

In Embodiment 3, the power supply state detection circuits PDETCn havecurrent detecting differential amplifier circuits 150 a to 150 f(hereinafter represented by 150 n), respectively. A current detectingdifferential amplifier circuit 150 n is a circuit for amplifying adifferential voltage across a current detection resistor 141 n connectedbetween a switching element 181 n and an electrical load 103 n with adifferential amplifier 151 n to generate a monitoring voltage Efnproportionate to a load current Ifn at the electrical load 103 n. Anon-inverting input terminal of the differential amplifier 151 n isconnected to a point of connection between the switching element 181 nand the current detection resistor 141 n through first and second seriesresistors 142 n and 152 n. A first negative voltage suppressing diode144 n is connected between a point of connection between the first andsecond series resistors 142 n and 152 n and the internal ground circuitGND2 of the power supply control unit 100C. An inverting input terminalof the differential amplifier 151 n is connected to a point ofconnection between the current detection resistor 141 n and theelectrical load 103 n through third and fourth series resistors 143 nand 153 n. A second negative voltage suppressing diode 145 n isconnected between a point of connection between the third and fourthseries resistors 143 n and 153 n and the internal ground circuit GND2 ofthe power supply control unit 100C. Thus, an excessively high negativevoltage applied to the differential amplifier 151 n when there is abreakage at the external common negative lines 104 x and 104 y for thecommutation diodes 146 n is suppressed by the first and second negativevoltage suppressing diodes 144 n and 145 n. This configuration ischaracterized in that damage to the differential amplifier 151 n by asurge voltage generated by the electrical load 103 n can be preventedwhen there is a breakage at the external common negative lines 104 x and104 y. The configuration is also characterized in that a surge currentsuperimposed on the internal ground circuit GND2 of the power supplycontrol unit 100C when a breakage occurs at the external common negativelines 104 x and 104 y can be suppressed to a very small value by thefirst and third series resistors 142 n and 143 n.

In Embodiment 3, the power supply control circuit PCNTC includes acontrol power supply circuit 110 and over-current detection circuits 350a to 350 f (hereinafter represented by 350 n). The control power supplycircuit 110 is configured to generate a stabilized control power supplyvoltage Vcc having a value lower than a driving power supply voltage Vbsupplied by the DC driving power supply 101. The power supply voltageapplied to a differential amplifier 151 n is the driving power supplyvoltage Vb. The monitoring voltage Efn output by the differentialamplifier 151 n is clamped to the level of the control power supplyvoltage Vcc by the voltage clamping diode 356 n. The over-currentdetection circuit 350 n is provided in association with each of theplurality of electrical loads 103 n to determine the presence of ashorting abnormality at the electrical load 103 n and a groundingabnormality at the positive side wiring 103P of the same detectingwhether the load current at the electronic load associated isexcessively large beyond a predetermined value. The over-currentdetection circuit 350 n includes a comparison circuit 351 n whichgenerates an over-current determination output when a voltage E0upstream of the monitoring voltage Efn obtained by the current detectingdifferential amplifier circuit 150 n exceeds a predetermined value equalto or higher than the control power supply voltage Vcc and provides thealarm signal OCn of the shorting abnormality generation to themicroprocessor 120C. This configuration is characterized in thataccurate current detection can be performed by clamping the monitoringvoltage Ef to the control power supply voltage Vcc at a normal maximumvalue of the load current and in that the over-current detection circuit350 n can be activated using the upstream voltage E0 when anover-current occurs.

In Embodiment 3, the abnormality processing means 811, 821, 831, and 841stop energization commands to the electrical loads and provide anabnormality notice not only when a breakage abnormality is detected atthe negative lines but also when either of a shorting abnormality at anelectrical load 103 n or a grounding abnormality at the positive sidewiring 103P of an electrical load 103 n is detected. The abnormalityhistory storing means 813, 823, 843, 833 a, and 833 b store and saveinformation on shorting abnormalities at the electrical loads 103 n andgrounding abnormalities at the positive side wirings 103P in the datamemory 123 in addition to the history of occurrence of breakageabnormalities. This configuration is characterized in that comprehensivehistory information can be stored in accordance with the contents ofabnormalities to facilitate maintenance and inspections because anenergization command to an electrical load 103 n is stopped and anabnormality notice is provided not only when there is a breakageabnormality but also when there is a shorting abnormality at theelectrical load 103 n or a grounding abnormality at the positive sidewiring 103P thereof.

OTHER EMBODIMENTS

In the above-described embodiments, the power supply state detectioncircuits providing inputs to the microprocessors 120A to 120C arecategorized into two types, i.e., a load current state detecting circuitand a load voltage state detecting circuit. A load current statedetecting circuit provides two types of signals, i.e., a monitoringvoltage Efn having an analog value proportionate to a load current Ifnmeasured by a current detecting differential amplifier circuit 150 n andan alarm signal OCn which is a logical signal obtained throughcompassion and determination at an over-current detection circuit 350 n.A load voltage state detecting circuit provides two types of signals,i.e., a load voltage measurement input Vfn having an analog valueproportionate to a load voltage detected by a load voltage monitoringcircuit 300 n and alarm signals OVn and SVn which are logical signalsobtained through compassion and determination at a load voltagemonitoring circuit 170 n. Embodiments 1 to 3 represent proper use ofsuch circuits in practical consideration to reduction of control burdenon a microprocessor and reduction in the number of analog inputs. Forexample, in Embodiment 2 shown in FIG. 6, the load voltage monitoringcircuits 300 n of the analog signal type may be replaced with the loadvoltage monitoring circuits 170 n of the comparison/determination typein Embodiment 1 shown in FIG. 2 to omit the determination of anover-resistance and the determination of an under-resistance which aredeterminations based on the software of a microprocessor.

A breakage abnormality can be detected using the over-resistancedetermination means constituted by step 440 in FIG. 4 or step 830 inFIG. 8 instead of using the negative line breakage abnormality detectioncircuits 160A to 160C. In the case of the over-resistance determinationmeans, the commutating function of the commutation diodes 146 a to 146 fis lost when a breakage occurs at the negative line. Therefore, anexcessively high load voltage is required to allow a target current Isnto be conducted. Consequently, there will be a state of over-resistancefrom which the breakage abnormality at the negative line will bedetected.

However, a problem remains in that the detected breakage abnormalitycannot be identified as none of a breakage at the electrical loads 103 ato 103 f, a breakage at the positive side wirings 103P or the negativeside wirings 103N, and a breakage at the external common negative line104, 104 x, or 104 y. For example, when a breakage abnormality hasoccurred at a particular electrical load, what is required is to stopthe energization command output to the same electrical load to ensuresafety, and there is no need for stopping the energization commandoutputs to all other electrical loads. In the case of a breakage at theexternal common negative line 104, 104 x or 104 y, it is required tostop the energixation command outputs to all electrical loads associatedwith the external common negative line to stop an induced surge voltageapplied to the switching circuits 130 n or 180 n quickly. Therefore,abnormality types must be separately detected.

Various modification and changes may be easily made to the invention bythose skipped in the art without departing from the scope and spirit ofthe invention, and it should be construed that the invention is notlimited to the embodiments illustrated herein.

1. A power supply control device for on-vehicle electrical loads,comprising a power supply control unit including a plurality of loadpower supply circuits for supplying power from a DC driving power supplyto a plurality of electrical loads respectively through switchingelements, a plurality of load commutation circuits for commutating loadcurrents to the electrical loads, and a power supply control circuit forsupplying an energization command output to the switching elements, andthe load power supply circuits, the load commutation circuits, and thepower supply control circuit being contained in a housing of the powersupply control unit, wherein: commutation diodes are provided in therespective load commutation circuits, and the commutation diodes areconnected in parallel with the respective electrical loads to causecurrents which has been flowing through the electrical loads to flowback when the switching elements of the load power supply circuits areturned off, and the commutation diodes are connected to a vehicle bodyoutside the housing separately from an internal ground circuit of thepower supply control unit by an external common negative line; the powersupply control circuit includes an individual abnormality detectioncircuit, a negative line breakage abnormality detection circuit,abnormality processing means, and abnormality history storing means; thepower supply control circuit is configured by using a microprocessor,and the microprocessor is configured to operate in conjunction with anon-volatile program memory in which at least a control program servingas energization command means for the switching elements is stored, adata memory, a RAM memory for arithmetic processes, and a multi-channelA-D converter; the individual abnormality detection circuit includes aplurality of power supply state detection circuits for detecting amountsof power supplied to the electrical loads and means for determining anindividual abnormal state when the amount of power supplied to a certainelectrical load among the electrical loads deviates from a target amountof supplied power, the individual abnormal state is either breakage orshorting of at least one of the certain electrical load, a positive sidewiring of the certain electrical load, a negative side wiring of thecertain electrical load, and the switching element associated with thecertain electrical load; the negative line breakage abnormalitydetection circuit is a circuit for determining a breakage abnormality ofthe external common negative line by detecting that an electricpotential on an anode side of each commutation diode is different froman electric potential at the internal ground circuit of the power supplycontrol unit; the abnormality processing means is means for stopping theenergization command output to the switching elements when at leasteither an individual abnormality or a breakage abnormality at theexternal common negative line is detected and for providing a notice ofthe abnormality; and the abnormality history storing means is means forstoring and retaining history of occurrence of individual abnormalitiesand breakage abnormalities at the external common negative line in thedata memory with identification of the abnormalities.
 2. The powersupply control device for on-vehicle electrical loads, according toclaim 1, wherein: voltage clamping diodes are connected to therespective switching elements to suppress an off-voltage thereof; thenegative line breakage abnormality detection circuit includes a seriescircuit including a constant voltage diode which starts conducting at avoltage lower than the clamping voltage of the voltage clamping diode, acurrent limiting resistor connected in series with the constant voltagediode, and a clip diode whose anode is connected to the internal groundcircuit of the power supply control unit, and a determination elementoperating in accordance with the state of energization of the seriescircuit; the series circuit is connected between the internal groundcircuit of the power supply control unit and an anode terminal each ofthe commutation diodes; and the determination element detects a breakageat the external common negative line according to an induced surgevoltage at the electrical load generated when there is a breakage at theexternal common negative line by detecting an electric potential at thecathode of the clip diode and supplies an alarm signal to themicroprocessor.
 3. The power supply control device for on-vehicleelectrical loads, according to claim 1, wherein: a bypass resistor isconnected in parallel with each of the commutation diodes; the negativeline breakage abnormality detection circuit includes a detectionresistor which is supplied with power from each of the bypass resistorthrough a block diode when there is a breakage at the external commonnegative line with the switching elements in an on-state, and adetermination element; and the determination element determines that abreakage has occurred at the external common negative line based on thefact that the detection resistor has been energized and supplies analarm signal to the microprocessor.
 4. The power supply control devicefor on-vehicle electrical loads, according to claim 1, wherein: theanode terminals of the commutation diodes are connected to the vehiclebody outside the housing through the external common negative line; aseparated ground connecting the external common negative line to thevehicle body is separated from at least a unit ground which connects theinternal ground circuit of the power supply control unit to the vehiclebody; and the distance between a load ground connecting negativeterminals of the electrical loads to the vehicle body and the separatedground is smaller than the distance between the unit ground and theseparated ground.
 5. The power supply control device for on-vehicleelectrical loads, according to claim 1, wherein: each of the powersupply state detection circuits has a current detecting differentialamplifier circuit, the current detecting differential amplifier circuitis a circuit for amplifying a differential voltage across a currentdetection resistor connected between the electrical load and theswitching element associated with the same with a differential amplifierto generate a monitoring voltage Ef proportionate to a load current Ifat the electrical load; a non-inverting input terminal of thedifferential amplifier is connected to a point of connection between theswitching element and the current detection resistor through first andsecond series resistors, and a first negative voltage suppressing diodeis connected between a point of connection between the first and secondseries resistors and the internal ground circuit of the power supplycontrol unit; an inverting input terminal of the differential amplifieris connected to a point of connection between the current detectionresistor and the electrical load through third and fourth seriesresistors and, and a second negative voltage suppressing diode isconnected between a point of connection between the third and fourthseries resistors and the internal ground circuit of the power supplycontrol unit; and an excessively high negative voltage applied to thedifferential amplifier when there is a breakage at the external commonnegative line for the commutation diodes is suppressed by the first andsecond negative voltage suppressing diodes.
 6. The power supply controldevice for on-vehicle electrical loads, according to claim 1, wherein:each of the power supply state detection circuits has a load voltagemonitoring circuit; the load voltage monitoring circuit includes eitheran analog input circuit which provides the microprocessor with the inputof a voltage proportionate to the load voltage applied to one of voltagedividing resistors connected between a point of connection between theelectrical load and the current detection resistor associated therewithand the internal ground circuit of the power supply control unit or acomparison/determination circuit which provides the microprocessor withthe input of the result of determination made by comparing the voltageproportionate to the load voltage applied to the one of the voltagedividing resistors with a predetermined threshold; and a clip diodewhose anode terminal is connected to the internal ground circuit isconnected in parallel with the one of the voltage dividing resistors tosuppress an excessively high negative voltage applied to the loadvoltage monitoring circuit when there is a breakage at the externalcommon negative line for the commutation diodes.
 7. The power supplycontrol device for on-vehicle electrical loads, according to claim 5,wherein: the microprocessor receives the input of an analog signal whichis the monitoring voltage Ef supplied from the current detectingdifferential amplifier and the input of an analog signal which is apower supply voltage measurement signal supplied from a power supplyvoltage measuring circuit; each of the power supply state detectioncircuits includes a comparison/determination circuit forming a loadvoltage monitoring circuit; the non-volatile program memory includes acontrol program including negative feedback control means which formsthe energization command means; the negative feedback control meanscontrols the turning on/off of the switching element by generating theenergization command output having a variable duty in accordance with anintegrated value of a deviation between an energization target currentIs for the electrical load and the load current If detected by a currentdetecting differential amplifier circuit; the power supply voltagemeasuring circuit includes a voltage dividing resistor for dividing adriving power supply voltage Vb provided by the DC driving power supplyand inputting the resultant voltage to the microprocessor; and the loadvoltage monitoring circuit includes a comparison/determination circuitwhich provides the microprocessor with the input of a determination madeby comparing a voltage proportionate to a load voltage applied to one ofvoltage dividing resistors connected between a point of connectionbetween the current detection resistor and the electrical load and theinternal ground circuit of the power supply control unit with apredetermined threshold.
 8. The power supply control device foron-vehicle electrical loads, according to claim 7, wherein: the powersupply control circuit includes leakage a resistor having a highresistance connected in parallel with the switching element and a loadvoltage dividing circuit provided on an output side of each of theswitching elements; the comparison/determination circuit includes firstand second comparison/determination circuits for comparing a voltageapplied to the one of the voltage dividing resistors of the load voltagemonitoring circuit with each of first and second threshold voltagesproportionate to the driving power supply voltage; the leakage resistorsupplies such a very small load current that the electrical load willnot be activated when the switching element is off; the load voltagedividing circuit includes a bypass resistor which is connected betweeneither a point connecting the switching element and the currentdetection resistor or a point connecting the current detecting resistorand the electrical load and either the anode terminal of the commutationdiode or the internal ground circuit of the power supply control unit;the first threshold voltage is proportionate to a voltage applied to thebypass resistor through the leakage resistor at the time of occurrenceof a breakage abnormality including a breakage at either the electricalload, or positive side wiring or negative side wiring of the electricalload; the second threshold voltage is proportionate to a voltage appliedto the bypass resistor at the time of occurrence of a shortingabnormality at the switching element and a power line shorting that thepositive side wire of the electrical load is contacted to a power supplyline; when a breakage abnormality occurs, the output logic of the firstcomparison/determination circuit is inverted to supply an alarm signalindicating the breakage abnormality to the microprocessor; and wheneither of a shorting abnormality at the switching element or a powerline shorting abnormality at the positive side wiring of the electricalload is occurred, the output logic of the secondcomparison/determination circuit is inverted to supply an alarm signalindicating either of the shorting abnormality at the switching elementor the power line shorting abnormality at the positive side wiring tothe microprocessor.
 9. The power supply control device for on-vehicleelectrical loads, according to claim 7, wherein: the non-volatileprogram memory includes a control program including load resistanceestimation means and at least either under-resistance determinationmeans or over-resistance determination means; the load resistanceestimation means performs a calculation to estimate a current resistancevalue of the electrical load, which is equivalent to γVb/If, based on anenergization duty γ of the energization command output provided by thenegative feedback control means, a driving power supply voltage Vbmeasured by the power supply voltage measuring circuit, and a loadcurrent If for the electrical load detected by the current detectingdifferential amplifier circuit; the under-resistance determination meansgenerates an abnormality determination output when the load resistanceestimated by the load resistance estimation means is smaller than aminimum load resistance in a low temperature environment, therebyproviding a notice of the occurrence of any of a shorting abnormality atthe electrical load, a grounding abnormality that is contact between thepositive side wiring and the vehicle body, and a shorting abnormality atthe switching element in the duration of the energization command forthe switching element; and the over-resistance determination meansgenerates an abnormality determination output when the load resistanceestimated by the load resistance estimation means is greater than amaximum load resistance in a high temperature environment, therebyproviding a notice of the occurrence of any of a breakage abnormality atthe electrical load, a breakage abnormality at the positive side wiring,a breakage abnormality at the negative side wiring, a power lineshorting abnormality that the positive side wiring of the electricalload is connected to a power supply line of the DC driving power supply,and a breakage abnormality at the switching element in the duration ofthe energization command for the switching element.
 10. The power supplycontrol device for on-vehicle electrical loads, according to claim 9,wherein: the under-resistance determination means further includesconfirmative determination means; and when the under-resistancedetermination means determines that there is a state ofunder-resistance, the confirmative determination means stores the factthat no shorting abnormality has occurred at the switching element asabnormality history information if the load current If has become zeroafter the energization command output to the switching element wasstopped.
 11. The power supply control device for on-vehicle electricalloads, according to claim 5, wherein: the power supply control circuitincludes negative feedback control circuit; the non-volatile programmemory includes a control program including target current command meanswhich constitutes the energization command means; a power supply voltagemeasurement signal which is an analog signal supplied by a power supplyvoltage measurement circuit and a load voltage measurement signal whichis an analog signal supplied by a load voltage monitoring circuit areinput to the microprocessor; the target current command means is meansfor generating a setting command output having a variable dutyproportionate to an energization target current Is for the electricalload; the negative feedback control circuit controls the turning on/offof the switching element by generating the energization command outputhaving a variable duty in accordance with an integrated value of adeviation between a set voltage Es proportionate to a target current Isobtained by smoothing the setting command output and a monitoringvoltage Ef proportionate to the load current If detected by the currentamplifying differential amplifier circuit; the power supply voltagemeasuring circuit includes a voltage dividing resistor for dividing thedriving power supply voltage Vb supplied by the DC driving power supplyand inputting the resultant voltage to the microprocessor; and the loadvoltage monitoring circuit is an analog circuit which supplies themicroprocessor with a load voltage measurement input proportionate to aload voltage applied to a voltage dividing resistor connected between apoint connecting the current detection resistor and the electrical loadand the internal ground circuit of the power supply control unit. 12.The power supply control device for on-vehicle electrical loads,according to claim 11, wherein: the power supply control circuitincludes a leakage resistors having a high resistance connected inparallel with the switching element and a load voltage dividing circuitprovided on the output side of the switching element; the non-volatileprogram memory includes a program including first and secondcomparison/determination means for comparing a load voltage obtained bythe load voltage monitoring circuit with each of first and secondthreshold voltages; the leakage resistor supplies such a very small loadcurrent that the electrical load will not be activated when theswitching element is off; the load voltage dividing circuit includes abypass resistor which is connected between either a point connecting theswitching element and the current detection resistor or a pointconnecting the current detection resistor and the electrical load andeither the anode terminal of the commutation diode or the ground circuitof the power supply control unit; the first threshold voltage isproportionate to a voltage applied to the bypass resistor through theleakage resistor at the time of occurrence of a breakage abnormalityincluding a breakage at any of the electrical load, the positive sidewiring of the electrical load, and the negative side wiring of theelectrical load; the second threshold voltage is proportionate to avoltage applied to the bypass resistor at the time of occurrence ofeither shorting abnormality at the switching element or the power lineshorting that the positive wiring of the electrical load is contacted toa power supply line; when the breakage abnormality occurs, the outputlogic of the first comparison/determination means is inverted to providea notice of the breakage abnormality; and when there is either shortingabnormality at the switching element or the power line shortingabnormality at the positive side wiring of the electrical load, theoutput logic of the second comparison/determination means is inverted toprovide a notice of the abnormality.
 13. The power supply control devicefor on-vehicle electrical loads, according to claim 11, wherein: thenon-volatile program memory includes a control program including loadresistance estimation means and at least either under-resistancedetermination means or over-resistance determination means; the loadresistance estimation means performs a calculation to estimate a currentresistance value of the electrical load, which is equivalent to Vf/Is,based on a load voltage vf measured by the load voltage monitoringcircuit and a target command current Is instructed by a target currentcommand means; the under-resistance determination means generates anabnormality determination output when the load resistance estimated bythe load resistance estimation means is smaller than a minimum loadresistance in a low temperature environment, thereby providing a noticeof the occurrence of any of a shorting abnormality at the electricalload, a grounding abnormality that is contact between the positive sidewiring and the vehicle body, and a shorting abnormality at the switchingelement in the duration of the energization command for the switchingelement; and the over-resistance determination means generates anabnormality determination output when the load resistance estimated bythe load resistance estimation means is greater than a maximum loadresistance in a high temperature environment, thereby providing a noticeof the occurrence of any of a breakage abnormality at the electricalload, a breakage abnormality at the positive side wiring, a breakageabnormality at the negative side wiring, a power line shortingabnormality that the positive side wiring of the electrical load isconnected to a power supply line of the DC driving power supply, and abreakage abnormality at the switching element in the duration of theenergization command for the switching element.
 14. The power supplycontrol device for on-vehicle electrical loads, according to claim 13,wherein: the over-resistance determination means further includesconfirmative determination means; and when the over-resistancedetermination means determines that there is a state of over-resistance,the confirmative determination means stores the fact that neither theshorting abnormality at the switching element nor the power lineshorting abnormality at the positive side wiring has occurred asabnormality history information if the load voltage Vf has dropped afterthe setting command output to the negative feedback control circuit wasstopped.
 15. The power supply control device for on-vehicle electricalloads, according to claim 7, wherein: the power supply control circuitincludes a control power supply circuit and an over-current detectioncircuit; the control power supply circuit is configured to generate astabilized control power supply voltage Vcc having a value lower thanthe driving power supply voltage Vb supplied by the DC driving powersupply; the power supply voltage applied to the differential amplifieris the driving power supply voltage Vb, the monitoring voltage Ef outputby the differential amplifier being limited to the level of the controlpower supply voltage Vcc by the voltage clamping diode; the over-currentdetection circuit is provided in association with each of the pluralityof electrical loads to determine the presence of a shorting abnormalityat the electrical load and a grounding abnormality at the positive sidewiring of the same by detecting whether the load current at theelectrical load associated is excessively high beyond a predeterminedvalue; and the over-current detection circuit includes a comparisoncircuit which generates an over-current determination output to supplyan alarm signal indicating the occurrence of a shorting abnormality tothe microprocessor when a voltage E0 upstream of the monitoring voltageEf obtained by the current detecting differential amplifier circuitexceeds a predetermined value equal to or higher than the control powersupply voltage Vcc.
 16. The power supply control device for on-vehicleelectrical loads, according to claim 11, wherein: the power supplycontrol circuit includes a control power supply circuit and anover-current detection circuit; the control power supply circuit isconfigured to generate a stabilized control power supply voltage Vcchaving a value lower than the driving power supply voltage Vb suppliedby the DC driving power supply; the power supply voltage applied to thedifferential amplifier is the driving power supply voltage Vb, themonitoring voltage Ef output by the differential amplifier being limitedto the level of the control power supply voltage Vcc by the voltageclamping diode; the over-current detection circuit is provided inassociation with each of the plurality of electrical loads to determinethe presence of a shorting abnormality at the electrical load and agrounding abnormality at the positive side wiring of the same bydetecting whether the load current at the electrical load associated isexcessively high beyond a predetermined value; and the over-currentdetection circuit includes a comparison circuit which generates anover-current determination output to supply an alarm signal indicatingthe occurrence of a shorting abnormality to the microprocessor when avoltage E0 upstream of the monitoring voltage Ef obtained by the currentdetecting differential amplifier circuit exceeds a predetermined valueequal to or higher than the control power supply voltage Vcc.
 17. Thepower supply control device for on-vehicle electrical loads, accordingto claim 1, wherein: the abnormality processing means stops energizationcommands to the electrical loads and provides an abnormality notice notonly when a breakage abnormality is detected at the negative line butalso when either of a shorting abnormality at each of the electricalloads or a grounding abnormality at the positive side wiring of each ofthe electrical loads is detected; and the abnormality history storingmeans stores and saves information on shorting abnormalities at theelectrical loads and grounding abnormalities at the positive sidewirings in the data memory in addition to the history of occurrence ofbreakage abnormalities.